Four 19th Century Latvian meteorite falls: Problematics of Mineralogical Reconst
Last Updated: 16th Oct 2015By Lon Clay Hill
Four witnessed 19th Century Latvian meteorite falls:
Historical, Linguistic, and Disciplinary Problematics of Mineralogical Reconstruction
Abstract
An extended discussion of the individual mineralites (minerals, mineral groupings, and sundry mineralogically phases ['items']) observed and recorded in 4 Latvian ordinary chondrite falls of the 19th Century is presented. 20 mineralites are discussed under four standard geochemical headings (silicates, Fe-Ni metal, sulfides, and oxides). A summary of the circumstances of these 4 witnessed falls, and a brief discussion of the problematics of reliably translating older observations into the proper contemporary terminology precede the core discussion. A selective bibliography is appended. While a primary focus of the text are some epistemological and linguistic issues associated with descriptions and classification, in-text links in the Table of Contents are provided for those interested in mineralogical specifics. Two small tables and one major table (Table C) included.
Notes:
'Municipality' - Latvia is currently organized into municipalities.
'Institution' — Location of university or academy housing the largest remaining mass. Additional info at MinDat location sites or the Catalogue of Meteorites (5/e).
Lixna mass - The 5.21 kg mass of Lixna listed with the Meteoritical Bulletin Database is the mass remaining after World War II. The larger original mass listed here appears both in the earliest reports and in several editions of the Catalogue of Meteorites, up to and including the 5th edition of 2000.
During the nineteenth century, the falls of four separate meteorites were observed and recorded in the small region of what is now the independent country of Latvia. No additional meteorite falls have been recorded in Latvia since that time. The timing and places of these four falls may strike us as a little odd, but statistical anomalies are frequently either merely statistical and/or undecipherable. What is more significance for science is that these falls were not only witnessed, but that significant portions of each meteorite have been preserved. Indeed, small samples are still occasionally used for current research (normally, however, only as one or data points on a long list). Even more important for both historical and scientific purposes, they were studied by scientists at some of the important museums and laboratories of the day during the century when the disciplines of chemistry, geology, physics and mineralogy were slowly emerging as separate discipline. For our purposes, it is important to note that the falls of these 4 meteorites occurred before X-rays were used to identify the unique atomic number of each element and the crystal structure of any sufficiently large mineral sample. These two developments, of course, are part of the assumed background for any contemporary discussion of either minerals or meteorites. For the past two years the author has been engaged in an effort to construct reasonably complete mineralogical inventories of scientifically and/or otherwise important meteorites and then post those findings in a publicly accessible venue (e.g.,'mindat.org'). There are, however, several factors that make the construction of such a mineral inventory a non-trivial task. What I wish to do here is state briefly some of the general problematics of my inquiry and then turn to the specifics of reconstructing the mineralogy of these four meteorites. I will then provide a critical assessment of both what has been accomplished and what still needs to be done.
TABLE B - QUICK MINERALOGICAL PROFILES FOR 4 LATVIAN CHONDRITES
M(N) is the composite tally for all MinDat recognized mineralites (or, 'items') [M] and IMA minerals [N], respectively.
A complete list w. citations for each meteorite is found at the individual meteorite's location site.
The intention here has been to provide a mineralogical profile listing those minerals and other mineralogically important constituents which have actually been observed in specific meteorites. By 'observed' we mean that the observation has been referenced by a suitable source. By 'minerals and other mineralogically important constituents', we mean both those minerals and mineralogical groups which have been accepted as such by the International Mineralogical Associations (IMA defined phases) and any other variety, chemically defined phase, or mineralogically significant item which is accepted by 'mindat.org' (MinDat) as a listable mineralogical 'item'. The first problem with the protocol used here is that, as a general rule, an author who reports his/her findings about any meteorite does not necessarily list all minerals which were observed in the meteorite. Specifically, an author may not report mineral phases which are normally present, but not relevant to the topic pursued. These general problematics are, however, amplified in several important ways in our particular inquiry into mineralogical composition of the four 19th Century Latvian meteorites. Most fundamentally, the terminology for classifying and describing both meteorites and minerals has undergone significant changes during the past two centuries. Frequently, today's observer uses different words to describe a mineralogical phase identical to the phase observed by the original observer. In some cases a mineral may have been observed which was not recognized as a distinct mineral at the time (troilite is a pertinent example). We can sometimes determine that a currently recognized mineral was originally observed and described using pre-discovery terminology — but in these cases we must proceed carefully. Another underlying issue is that geochemical issues sometimes blunt mineralogical specificity in contemporary meteorite research. For example, mixed chemical-mineralogical terms (e.g., Ca-poor pyroxene) or bare chemical descriptors (e.g., silica, sulfide, silicon carbide) are simply unacceptable in many formal mineralogical venues including — at times — even MinDat with its more latitudinarian protocols. Such terms, however, are both ubiquitous and standard in contemporary meteorite research with its frequent dominantly geochemical focus. With these considerations in mind let us turn to some considerations of our four ordinary chondrites as a whole and then turn to the specific mineralogical phases which are present in one or more of the four 4 meteorites.
Classification of all meteorites are in actuality determined by an assemble of chemical, isotopic, textural, and mineralogical criteria which have developed over time. For our purposes we wish to express succinctly the relationship between the contemporary formalism as expressed at The Meteoritical Society's 'Meteoritical Bulletin Database' website and the mineralogical expectations for the ordinary chondrites considered here. All meteorites are unique (idiosyncratic) to some degree and there are always debates and revisions concerning the proper limits of every meteorite class, type or subtype. Some simplifying features for our four meteorites are that (1) as H- and L-chondrites they fit neatly into the norm of two of the most stable classification categories utilized by meteoriticists. These four meteorites are neither 'anomalous' nor 'borderline' H or L chondrites. (2) They are all witnessed falls and essentially 'unweathered'. And, finally, (3) their masses were sufficiently large as to minimize some of the inherent sampling problems encountered with very small samples (all chondrites are inhomogeneous at the smallest scales). Ordinary chondrites are formally defined by bulk elemental ratios, oxygen isotope ratios, and some subordinate textural/mineralogical criteria — items consistent with their original formation on small asteroidal bodies and their near solar-like chemistry for their non-volatile constituents. We focus here, however, on their expected mineralogical characteristics.[1]
We assume here that any sufficiently large and unweathered and properly classified ordinary chondrite contains olivine, pyroxene, and Fe-Ni metal. To be sure, we can also add that we would almost always expect to find troilite, small amounts of plagioclase and/or glass of plagioclase composition, and accessory chromite. Minor phosphates are usually to be expected as well. There is nothing particularly new here. The distinguishing mineralogical features of ordinary chondrites were succinctly summarized by Brian Mason several decades ago in one of his many American Museum Novitates (Mason, 1962)[2]. Our concern here is of a different nature. We are trying to establish a protocol to identify those mineralogical phases (mineralites) which have been specifically observed and, in some sense, recorded. We are not trying to identify those mineralites that are highly likely to be present or, even, almost certainly present. We will start by assuming that any unweathered meteorite which has been properly classified as an ordinary chondrite contains olivine and pyroxene. Others might wish to assume that, say, all properly classified H chondrites contain kamacite and that all petrologic type 6 H and L chondrites contain orthopyroxene. Perhaps. I think the case for assuming that all H6 and L6 chondrites contain orthopyroxene seems almost implied by definition. However, the observations are not really reported with that much mineralogical specificity. And, there is an advantage in waiting for more specific mineralogical reports. Detailed examination often reveals that our 'expected phases' are frequently accompanied by some unexpected phases.
There is an even more important reason for caution. Ordinary chondrites have normally experienced one or more serious shocks while in space and during their atmospheric entries. These shocks sometimes introduce significant mineralogical changes — transforming some phases into other phases. These shocks may effect the petrological type of a meteorite but they would not normally effect the meteorite's identity as a member of a defined chemical group (in this case, H or L-chondrite). And, our inventory is especially dependent upon the observer's equipment and skills. The presence of phases such as ilmenite, copper, and isocubanite in the mineral lists for Buschhof and Lixna is due to the fact that the eminent Paul Ramdohr investigated these meteorites with a petrographic refractor. Other instruments - such as the otherwise eminently useful microprobe - are not as helpful in uncovering the presence of these particular species unless the researcher targets such phases and has special skills. Before parsing our inventory, we note that because all the Latvian ordinary chondrites are of petrologic types 4-6, we begin with the fact that all of these meteorites have equilibrated or almost entirely equilibrated olivine. Secondly, the Fe-Ni metal in L chondrites is more Ni-rich than the Fe-Ni metal in H chondrites. Thus, a priori, one would expect taenite to be more readily observed in L- chondrites than in H-chondrites (all else being equal). Finally, we note here that three of the Latvian meteorites are described as veined in the latest edition of the Catalogue of Meteorites (5/e)[Grady, 2000]. The veins are normally due to pre-terrestrial shocks (or, occasionally, to fractures during atmospheric entry). Shocks also create glass and crystal twinning which may persist until eventually meteorite recovery. Thus we will start by assuming that olivine and pyroxene are present and consider all other mineralites on a case-by-case basis.[3]
These are the specific minerals and mineralogically significant items of our discussion. By definition the 10 International Mineral Association (IMA) minerals do not overlap with each other. However, other inclusive and overlapping categories such as mineral groups and series may be redundant in particular instances. Please note, also, that 'Fe-Ni metal' — the currently preferred term in most meteoritics literature — is not a MinDat category. Vide infra!
Table C: 20 Reported Minerals & Mineralites in 4 Latvian Chondrites
Minerals, Mineral Groups,Mineral Subgroups,Mineral Series,Mineral Varieties, Chemically Defined Aggregates, Glass
TABLE C CATEGORIES:
Mineralite&Host#= Mineral/Mineralite (with number of meteorite hosts in parenthesis)
TERMINOLOGY
Olivine and Plagioclase are 'Solid solutions series'
Pyroxene is a 'Mineral Group' with 'Subgroups' Orthopyroxene and Clinopyroxene.
'Diallage' is a variety of Diopside.
Plagioclase is treated as an exact synonym for the "Albite-Anorthite Series" by MinDat algorithms.
We proceed along lines of standard geochemical categories and then, roughly, by number of meteorite hosts. We say, roughly, because overlapping categories used in describing mineralites need to be disentangled as we proceed. As a preliminary note, we note the observed occurrences of olivine, pyroxene, plagioclase, Fe-Ni metal, troilite, and chromite in all 4 Latvian chondrites. We have listed these 6 mineralites, roughly, in order of volume abundance. The relative proportions of Fe-Ni metal and troilite, in particular, are not constant.
Olivine reported in all 4 meteorites.
Pyroxene reported in all 4 meteorites.
Orthopyroxene (2) reported in Misshof and Lixna.
Clinopyroxene (2) reported in Misshof and Lixna.
Plagioclase reported in all 4 meteorites.
Glass is reported only in Misshof.
OLIVINE
Olivine is usually the most abundant mineral in ordinary chondrites. The olivine is prominent in both chondrules and in the more comminuted in matrix. Indeed, for decades meteorites which are now labelled as H and L chondrites were called 'Olivine-bronzite' and 'Olivine-hypersthene' chondrites, respectively. As a procedural matter, since exhaustive mineralogical observations have not always been explicit reported in Meteoritical Bulletins and in the various versions of the Catalogue of Meteorites, this author assumes as a procedural protocol that olivine has been observed in any meteorite which has been classified as either an 'Olivine-bronzite' or 'Olivine-hypersthene' chondrite in any edition of the Catalogue of Meteorites complied by the Natural History Museum (London) editors. In this case, the classification information is actually redundant since Brian Mason reported the composition of all 4 Latvian meteorites in 1962. In addition, his observations also indicated that the olivine in each of the meteorites is equilibrated.
PYROXENE
Pyroxene is always an abundant component in ordinary chondrites in both chondrules and matrix. The H and L chondrites were previously called 'Olivine-bronzite' and 'Olivine-hypersthene' chondrites. In most cases the dominant pyroxene is Ca-poor orthopyroxene, but there are exceptions. The primary complicating factor is that quickly cooled and/or shocked pyroxene may be partially or predominantly clinopyroxene. Again, as a procedural matter, this author assumes as a procedural protocol that pyroxene has been observed in any meteorite which has been classified as either an 'Olivine-bronzite' or 'Olivine-hypersthene' chondrite in any edition of the Catalogue of Meteorites. If the meteorite has not been seriously altered by shock, we could usually assume that almost all of the pyroxene in a petrologic type 6 ordinary chondrite is almost entirely orthopyroxene. However, the author normally requires a specific reference. A minor constituent in many ordinary chondrites are the two Ca-rich clinopyroxenes, augite and diopside.
Two problematics are relevant to our inquiry. It is only around the end of the 19th Century that consistent differentiation between augite or diopside as presently understood and other clinopyroxenes could be made on a consistent basis. Thus, for example, the "schwarzen Augit" [black augite] reported in Lixna by Kuhlberg (1865) is evidently 'clinopyroxene' and is so listed. However, it is unclear to this author whether the actual IMA defined species was pigeonite, diopside or augite. See Farrington (1915) for additional insight into the development of 19th Century pryoxene understanding. Developments of the last few decades have also altered the reporting of pyroxene mineralogy within the meteoritical literature. While the Latvian meteorites have not been scrutinized in great detail in recent decades, what current interest there is may be reported in geochemically focused venues which often suppress explicit attention to mineralogical detail. Current reports routinely note the presence of 'Ca-rich pyroxene' , but the actual per se detection of augite and/or diopside and/or pigeonite is not always a matter of interest. In many of these cases it is actually difficult to imagine that we are dealing with anything besides a 'clinopyroxene' — most likely diopside or augite (with hedenbergite an outside possibility).
Orthopyroxene is clearly present in both Lixna (H4)and Misshof (H5). We would expect that the two H6 chondrites Buschhof and Nerft would also have orthopyroxene, but unambiguous evidence is lacking. Clinopyroxene is also present in Misshof as diallage, a variety of diopside, and in Lixna.
PLAGIOCLASE
Plagioclase ('Albite-Anorthite Series' @MinDat) is a normal accessory component of almost all ordinary chondrites in both chondrules and matrix. And, indeed, plagioclase has been reported for all 4 Latvian chondrites so the general picture seems to be more or less as expected. We mention two minor complications which are not resolved here. Most ordinary chondrites have been at least mildly shocked on several occasions between original aggregation on the original parent body (OPB) and their eventual impact with the earth. Plagioclase is more easily converted to glass than either pyroxene or olivine so that some residual glass of plagioclase composition ('maskelynite') is usually present to some extent in ordinary chondrites. For type 4-6 chondrites most or all of the glass was devitrified by metamorphism on the OPB. The long journey between the OPB and the earth, however, created additional opportunities for the creation of glass.
GLASS
The apparent presence of glass in Misshof would presumably be due to late shock. Primary glass has been devitrified in Type 4-6 silicates, but secondary glass can be created by impact at any time. As three of the Latvian meteorites are described as 'veined' it is somewhat surprising that this author was able to find only one seemingly unmistakable reference for the glass. Perhaps someone with more knowledge of German and petrographic history can shed additional light on this subject.
SILICATE SUMMARY
As far as the principle silicates (olivine, pyroxene, and plagioclase), the outlines of our records are more or less as they should be. However, it is somewhat disappointing that more precise information about the intricate interplay between orthopyroxenes and clinopyroxenes is quite sparse.
TERMINOLOGY
We should also note that — while usage differs — there is a strong preference within many members of the meteoritical community to avoid the use of the term 'Feldspar' unless there is a strong potassium component within the usually Na- and or Ca- dominated mineral. On first impression it appear that most — if not all — of the 'Feldspar' reported here was in fact K-poor — i.e., 'Plagioclase' and thus we have listed it.
Fe-Ni Metal (or, 'Meteoritic Iron') is found in all 4 Latvian meteorites.
Kamacite (3) is specifically reported for Buschhof (L6), Lixna (H5), and Misshof (H5).
Taenite (2) is specifically reported for Buschhof (L6) and Misshof (H5).
Copper (2) is reported for Buschhof (L6) and Lixna (H5).
In most early reports of Fe-Ni metal in ordinary chondrites, the presence of unoxidized or 'free' Ni-bearing iron ['Nickeliferous iron'] became the recognized signature for almost all meteoritic materials as it clearly differentiated meteorites from any natural or terrestrial artificial heavy iron-ores and/or masses known at the time. Once the techniques of preparing polished surface became common, at least at research institutions, the use of a petrographic reflecting microscope enabled Reichenbach and others to differentiate between the merely Ni-bearing kamacite (Ni ~5-7%) and the Ni-rich taenite (Ni ~15-30%). X-ray crystallography later confirmed the mineralogical validity of the crystallographic distinction between the body-centered cubical kamacite and the face-centered taenite. It has now been known for over a century that most of the Fe-Ni metal found in ordinary chondrites has been partitioned into two phases. There are several second-order complications which we mention here, but they are — for the purposes of our current discussion which is restricted to 4 unweathered, moderate-sized ordinary 'ordinary chondrites' with equilibrated olivines— quite tractable. We have included elemental copper in our somewhat elastic geochemical grouping as it does not deserve a separate category.
Fe-Ni Metal
As our first consideration, then, we need to define some terms. 'Fe-Ni metal' is the current term of choice for the Ni-bearing iron invariably found in all iron-rich meteorites and in almost all chondritic meteorites. This Fe-Ni metal also contains cobalt (usually 0.3-1.0%) and lesser amounts of chromium and phosphorus. Now it should be understood that the term 'Fe-Ni' metal is not mineralogically neutral. As applied to ordinary chondrites, it contains the implicit understanding that in all likelihood — with some exceptions noted below — all or nearly all of the Fe-Ni metal is either kamacite and/or taenite. To be sure, minor amounts of other Fe-Ni metal phases have been reported from other ordinary chondrites — e.g., plessite and tetrataenite — but the author is unaware of such citations for the Latvian meteorites in the literature he has examined. For other meteorite classes, other considerations obtain. Thus, for example, in meteorites derived from the cores of larger, more slowly cooled parent bodies (irons, pallasites) and from highly shocked meteorites, other Fe-Ni rich metallic phases are sometimes found in significant quantities. But, these complications are not in evidence here.
The term 'Meteoritic Iron' used at MinDat is a close synonym for 'Fe-Ni metal' but it is a mineralogically neutral term. In the meteoritic literature, 'Fe-Ni metal' may be used because the author is not particularly concerned about explicit mineralogical terms and may not put in print what he or she has already observed. 'Meteoritic Iron' is actually a somewhat more positive label — at least as I read the term — as it normally means that the author has observed no convincing evidence for any definite Fe-, Ni-rich metallic phase. For example, stand alone microprobe observations often produce little (if any) per se mineralogical data.
KAMACITE & TAENITE
We can expand on what is known about kamacite and taenite in ordinary chondrites. As a first consideration, we note that the amount of Fe-Ni metal available for each of would be expected to variable. First, we discovered and have thus defined the two classes by the amount of total iron available — H (high-iron) ordinary chondrites and L (low-iron) ordinary chondrites. Secondly, within the two groups, there was some natural variability in original composition, in oxygen fugacity, sulfur abundances, and in cooling rates. However, thirdly, and most important for our discussion is that the oxygen fugacity for the L chondrites was significantly higher than for H chondrites. Subsequently, more iron preferentially entered the silicate phases (olivine and pyroxene) leaving the metallic phases more Ni-rich. Consequently, the fraction of taenite in L chondrite metal is actually higher than in H chondrites.
Thus, there is no surprise in the fact that some form of Fe-Ni metal has been reported for all 4 Latvian meteorites — either as kamacite and/or taenite or as 'meteoritic iron'. The simple 'meteoritic iron' reported for Nerft (L6), however, comes with some additional information. It is reported as consisting of 20% nickel. One suspects that the Fe-Ni metal is taenite. If so, then both L6 meteorites would contain taenite. Of course, the fact that taenite is reported for both one H5 fall and one L6 fall is not really too surprising.
Our overall inventory of Fe-Ni metal in the Latvian meteorites is thus somewhat as we might expect. However, much of this is due to the fact that, first, a great observer made an extensive study of the opaques in two of the meteorites and, secondly, a modern investigation by Guignard & Toplis (2015) has filled in some of the blanks for Misshof.
COPPER
The presence of copper in two Latvian meteorites is not surprising in itself. Copper is a ubiquitous, but very minor constituent in many ordinary chondrites. However, detecting copper is not a trivial observation. The two citation we have are both derived from Ramdohr's observation published just over 4 decades ago [Ramdohr, 1973]. Ramdohr was a maestro both of ore mineralogy and of reflected light microscopy. Today, in somewhat similar fashion, one notes the coincidental reports of meteorite copper in some of Alan Rubin's work — but one does not look for it in the average 'semi-complete' petrographic description.
Troilite (4) — Troilite is reported for all 4 meteorite, usually by several observers.
Isocubanite (2) — Isocubanite (labelled 'Chalkopyrrhotite') was observed in Buschhof (L6) and Lixna (H4) by Ramdohr (1973).
Mackinawite (1) — Mackinawite was observed in Buschhof by Ramdohr (1973).
Schreibersite (2) — Schreibersite has been observed in both Lixna (H4) and Nerft (L6).
SULFIDE & PHOSPHIDE SUMMARY
Our reported inventory of sulfides and phosphides is certainly what we night expect from a brief foray into the mineralogical thicket of sulfides and phosphides. Both troilite and schreibersite were first discovered in meteorites and are ubiquitous components of many meteorite classes including — most notably — ordinary chondrites and irons. Sulfides are, of course, common in a number of terrestrial ores, but they tend to be turned into sulfates when they get close to the earth's more oxidizing crustal environment. Phosphides are extremely rare in terrestrial environments as terrestrial phosphorus is almost always found either as phosphate or as a, usually, minor component in various uncommon minerals. We would expect troilite to be present in any unweathered ordinary chondrite — and, indeed, we would be very surprised if troilite were not present in these 4 Latvian meteorites. The case for schreibersite is a little different. Schreibersite is commonly found in association with Fe-Ni metal and/or with troilite in ordinary chondrites, but is not always particularly abundant. There is, however, one complication that we must address directly. Troilite and schreibersite were first recognized as distinct minerals during the 19th Century. Thus, we will need to determine if whether pre-discovery observations of these phase were made before our current labels were used.
Pyrite had been used as a generic term for iron sulfides since the middle ages and only gradually became the specific term for one of our most common terrestrial iron sulfides. The cubic (isometric diploidal) crystal structure was obvious enough and the chemical parameters developed in due time. By the middle of the 19th Century pentlandite had been identified at Sudbury. Pentlandite is also isometric, but it tends to form massive aggregates and so its somewhat different crystal structure had not been so immediately obvious as that of pyrite. Its chemical affinity for Ni is also important as its enhanced Ni content differentiates pyrrhotite from the other iron sulfides we discuss here. In 1863 troilite was discovered in the Albareto chondrite. Troilite was clearly distinguishable both mineralogically (hexagonal) and chemically (stoichiometric FeS). Like pyrite, troilite is also non-magnetic. It gradually became clear that troilite was in fact the most common meteoritic iron sulfide. An additional complication arose, however, which effects our reading of the mineralogy of Latvian meteorites. Another hexagonal, but magnetic terrestrial iron sulfide was discovered also discovered about this time — pyrrhotite. It was sometimes referred to as 'magnetic pyrite' and, apparently, sometimes is still referred to by this term. In fact, however, we can also think of pyrrhotite as a hexagonal iron sulfide with an FeS1-x composition which 'becomes' non-magnetic troilite if x =0.
We must apply an important physical principle is in order to utilize our 19th Century records — oxygen fugacity (a measure of an elements 'activity' or, crudely, effective 'pressure'). While the abundance of sulfur is, of course, important, how iron interacts with sulfur is also quite dependent upon the activity of oxygen. When sufficient oxygen is available iron readily forms strong and stable Fe-O bonds and less iron is available to form sulfides. Of course, in many terrestrial environments almost all sulfur is found as sulfate. However, pyrite (FeS2) is the most common iron sulfide in many crustal environments. Pyrrhotite and pentlandite are also encountered in a number of moderately reduced terrestrial environments. During the early part of the 19th Century iron-sulfide in meteorites was almost invariably described as 'pyrite'. In 1863 it was determined that the iron sulfide in the Albareto chondrite was not pyrite. Troilite was clearly distinguishable mineralogically (hexagonal) and chemically (stoichiometric FeS). Troilite is also non-magnetic. Troilite has since been found in some very unusual terrestrial environments such as coal dumps as it is hexagonal Pyrite heretofore described 'pyrite crustal environments almost all sulfur is found as sulfate.
TROILITE
The case of troilite is mildly complicated but quite tractable. After is discovery in 1863, the term troilite gradually became standard, but adoption was sporadic. In 1884 Fremy referred to 'Pyrrhotine' in describing Nerft. In 1916 Merrill referred to 'Pyrrhotite' in describing Misshof. There is, however, no good reason to think that anything other than troilite is being described in these two meteorites. The German term "Magnetkies"— the current label for pyrrhotite — is also encountered with reference to troilite. With its shared hexagonal crystal symmetry and the chemical standards of the late 19th and early 20th it would have been either impossible or almost impossible to differentiate the two minerals. Etymologically, "Magnetkies" refers to pyrrhotite's weak magnetism. But demonstrating troilite's lack of a magnetic field in the presence of Fe-Ni metal a century or more ago is difficult to imagine in most circumstances. As long as we are discussing an unweathered, properly classified moderately equilibrated ordinary chondrite the dominant Fe-sulfide would always be troilite. Of course, a focused contemporary study of the micro-phases within the shock-melted veins of moderately or severely shocked ordinary chondrites could very well uncover some minor mineralogical deviations.
ISOCUBANITE
Ramdohr (1973) described isocubanite (synonym, isochalcopyrite) under the label 'Chalkopyrrhotite' in both Buschhof (L6) and Lixna (H4). Isocubanite is an isometric polymorph of cubanite which was formally recognized in 1988 by the IMA. It had apparently been recognized for a few decades as one of several phases or varieties of iron-copper sulfides found in certain terrestrial ores. While it is an invariably very minor constituent of stony meteorites, Ramdohr recognized its presence in nearly half of the 400 meteorites which he examined with a petrographic reflecting microscope.
MACKINAWITE
Ramdohr (1973) described mackinawite in Buschhof (L6) and Lixna (H4). Mackinawite is a tetragonal Fe-Ni sulfide formally recognized in 1962. While it appears to be an invariably very minor constituent of stony meteorites, Ramdohr recognized its presence in a significant number of stony meteorites. which he examined with a petrographic reflecting microscope. While it appears to be an invariably very minor constituent of stony meteorites, Ramdohr recognized its presence in over 90 stony meteorites of the roughly 400 meteorites which he examined with a petrographic reflecting microscope.
SCHREIBERSITE
Schreibersite is reported in both Lixna (H4) and Nerft ['Phosphornickeleisen' in Kuhlberg, 1865's description of Lixna]. This is not too surprising. Schreibersite is a common, but minor accessory in meteorites. As phosphorus is an order of magnitude more scarce in the solar system than sulfur we would not expect as a major role for phosphides. Even more importantly, phosphorus is more easily oxidized than sulfur. [Electronegativity of phosphorus is only 2.19 compared to Sulfur's 2.58, Cf. Emsley (1998),Elements (3/e)]. In fact, phosphates are frequently found even in iron meteorites where we would never expect to observe sulfates. In both older and newer meteoritical literature, there are frequent reports of phosphates or even Ca-phosphates — but these reports are mineralogically indeterminate. As a matter of fact — with, of course, some interesting exceptions — the great bulk of meteoritic phosphate minerals are almost always either apatite or merrillite (aka, whitlockite). Merrillite is essentially anhydrous whereas apatite normally carries a mixture of hydroxyl, chorine, and/or fluorine ions. For now we simply observe that — except when a special effort is made to find phosphates for, say, their radiogenic isotopes — both phosphide and phosphate minerals will be largely unnoticed and thus underreported in meteoritical studies of both old and more recent falls.
In a larger sample of thoroughly studied ordinary chondrites we, of course, find numerous additional instances of sulfides, carbides, and phosphides which are much rarer in oxidizing environments. However, as phosphorus is an order of magnitude more scarce in the solar system than sulfur we do not normally expect phosphides in great abundance in any ordinary chondrite.
Chromite (4) - Reported in all 4 Latvian meteorites, usually by more than one observer.
Ilmenite (1) - Reported in Lixna by Ramdohr (1973).
Oxides other than magnetite and chromite are not usually found in abundance in ordinary chondrites, but they are not necessarily rare. Ilmenite, rutile, spinel, and some silica polymorphs are occasionally reported. They may, however, require special lithological conditions and special observational attention before being reported. Silica polymorphs, for example, show up in quickly cooled inclusions which are out of equilibrium with the always abundant olivine. As no specific phosphates or carbonates have been noted in the reports cited here, we will forego any discussion of those phases. Likewise, it could very well be that the chromite reported here may have included instances of Ti-rich or Al-rich varieties which are not 'chromite' sensu strictu, but we will also forego that discussion.
CHROMITE
Chromite is the most common member of the spinel group to occur in ordinary chondrites. Thus it is not too surprising that it is reported for all four Latvian meteorites. It is, however, mildly surprising that magnetite has not been reported. Magnetite is both a ubiquitous component within the fusion crust of most meteorites and an occasional pre-terrestrial constituent of the original mineralogical assemblages of many chondrites.
ILMENITE
Ilmenite grains or exsolution lamellae in chromite are commonly found when time, proper equipment, and patience are present. The fact that its presence has not been reported for the other 3 meteorites besides Lixna does not mean that it is not present in one or more of them.
Combining observations made over the past two centuries we can reconstruct a reasonable outline of the primary mineral phases found in the 4 Latvian chondrites that fell in the 19th Century. The primary expected constituents — olivine, pyroxene, plagioclase, Fe-Ni metal, and troilite — have all been observed on one or more occasions (usually more than once) in all four of these ordinary chondrites. Accessory chromite was also found in all four meteorites. A few additional minor phases were found within one or more meteorite hosts (copper, isocubanite, mackinawite, Ilmenite, schreibersite). Most gratifying from a procedural perspective is that there appears to be no contradiction to our initial assumption that — for unweathered meteorites whose original parent bodies were, by terrestrial standards, environments of extremely low oxygen fugacity — we can successfully decode descriptions of troilite which were written before troilite had been recognized as a separate mineral.
There remain some outstanding issues. The Latvian pyroxene assemblages are almost certainly underreported. Pigeonite is not explicitly reported here in a single instance and diopside is only reported once. The descriptions of Fe-Ni metal also appear somewhat incomplete. While phosphorus is reported in some chemical assays, no specific phosphate minerals are reported here (schreibersite does appear twice). It may be that someone who has more complete access to the German literature (or is a more fluent reader than the author) could provide additional mineralogical information about the 4 meteorites. There could also be additional information about these meteorites in Slavic language venues (historical or modern) which this author is unable to understand. Perhaps some readers can make a contribution.
And in any case, we can always hope — and, when possible, insist — that a thorough report of a meteorite's mineralogical constituents are a necessary component of the information profile of any meteorite large enough to classify or important enough to study.
The Bibliography includes most major sources utilized in constructing the mineral lists for the 4 Latvian ordinary chondrite falls. It also provides several standard sources referred to in the text — particularly those which deal with the interplay between meteorite classification and mineralogy. The bibliography is provided into two frameworks — a standard alphabetical order for ease of use and a timewise order consistent with the fundamental historical approach of the article. A number of the older books are also available as free Google e-books. While there are a number of digital citations at the 4 individual Mindat location sites for the 4 meteorites, I have restricted my e-bibliography here to the minimum needed for quick access to the Meteoritical Bulletin Database which has immediate links to the SAO Astrophysical Data System and to Google. Most interested readers have their own procedures for accessing the World Wide Web and are usually more savvy than I.
E-Biblio Links to 'Meteoritical Bulletin Database
http://www.lpi.usra.edu/meteor/metbull.php - Meteoritical Bulletin Database
http://www.lpi.usra.edu/meteor/metbull.php?code=5178 -Buschhof@MetBullDatabase
http://www.lpi.usra.edu/meteor/metbull.php?code=14670 -Lixna@MetBullDatabase
http://www.lpi.usra.edu/meteor/metbull.php?code=16703 -Misshof@MetBullDatabase
http://www.lpi.usra.edu/meteor/metbull.php?code=16945 -Nerft@MetBullDatabase
BIBLIOGRAPHY ABC…
Alexeev, V. A. (1988) Parent bodies of L and H chondrites: Times of catastrophic events. Meteoritics & Planetary Science 33 (1): 145-152. (March 1988).
Doss, B. (1891) Der Meteorit von Misshof in Kurland. IN Arbeiten des Naturforscher-Vereins zu Riga (7):1-68.
Emsley, J. (1998) The Elements (3/e). Clarendon Press: Oxford. 294 pages.
Grady, M.M. (2000). Catalogue of Meteorites (5/e). Cambridge University Press: Cambridge; New York; Oakleigh; Madrid; Cape Town. 689 pages.
Grady, M.M., Pratesi, G. & Moggi-Cecchi, V. (2015) Atlas of Meteorites. Cambridge University Press: Cambridge, United Kingdom. 373 pages.
Graham, A. L., Bevan, A. W. R. & Hutchison, B. (1985) Catalogue of Meteorites (4/e). University of Arizona Press: Tucson.
Grewingk, C. & Schmidt, C. (1864) Ueber die Meteoritenfälle von Pillistfer, Buschhof und Igast in Liv-und Kurland. Heimrich Laakmann: Dorpat.
Guignard, J. & Toplis, M. J. (2015) Textural properties of iron-rich phases in H ordinary chondrites and quantitative links to the degree of thermal metamorphism: Geochimica et Cosmochimica Acta 149: 46-63. (Jan 2015).
Farrington, O. C. (1915) Meteorites: Their Structure, Composition, and Terrestrial Relations. The Lakeside Press, R. R. Donnelley & Sons Company: Chicago.
Hutchison, R. (2004) Meteorites: A Petrologic, Chemical and Isotopic Synthesis. Cambridge University Press: Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo. 506 Pages.
Kuhlberg, K. (1865) Analyse und Beschreibung der Meteorite von Nerft, Honolulu, Lixna und eines im Gouvernement Jekatherinoslaw gefallenen Meteoriten. Heimrich Laakmann: Dorpat.
Mason, B. (1962) The Classification of Chondritic Meteorites. American Museum Novitates, No.2085. New York, 1962, 20 pp.
Mason, B. (1963) Olivine Composition in chondrites. Geochimica et Cosmochimica Acta 27: 1011-1023.
Merrill, G. P. (1916) Handbook and Descriptive Catalogue of the Meteorite Collections in the U.S. National Museum. Bull. U. S. Natl. Museum, No.94, Washington. 207 pp., 41 pls.
Meunier, S. (1884) Météorites: In Encyclopédie chimique: Métalloïdes, vol II (Fremy, M., editor). Dunod: Paris.
Poggendorf, J.C. (1852) Annalen der Physik un Chemie. JA Barth: Leipzig.
Prior, G.T. (1916) On the remarkable similarity in chemical and mineralogical composition of meteoritic stones: Mineralogical Magazine 17 (78):38. (April 1916)
Prior, G.T. (1923) Catalogue of Meteorites: with special reference to those represented in the collection of the British Museum of Natural History. Richard Clay & Sons, Limited: Bungay, Suffolk.
Ramdohr. P. (1973) The Opaque Minerals in Stony Meteorites. Elsevier Publishing Company: Amsterdam; London: New York. 245 pages.
Rubin, A. E., Peterson, E., Keil, K., Rehfeldt, A. & Jarosewich, E. (1983) Fragmental breccias and the collisional evolution of ordinary chondrite parent bodies: Meteoritics 18(3): 179-196. (30 Sept 1983).
Yudin, I. A. (1970) Microscopic study of the Buschhof stony meteorite: Meteoritika, Vyp. (No.) 30, p. 88 - 92. (In Russian).
[End of ABC Bibliography]
BIBLIOGRAPHY (Temporal Order)
Poggendorf, J.C. (1852) Annalen der Physik un Chemie. JA Barth: Leipzig.
Grewingk, C. & Schmidt, C. (1864) Ueber die Meteoritenfälle von Pillistfer, Buschhof und Igast in Liv-und Kurland. Heimrich Laakmann: Dorpat.
Kuhlberg, K. (1865) Analyse und Beschreibung der Meteorite von Nerft, Honolulu, Lixna und eines im Gouvernement Jekatherinoslaw gefallenen Meteoriten. Heimrich Laakmann: Dorpat.
Meunier, S. (1884) Météorites: In Encyclopédie chimique: Métalloïdes, vol II (Fremy, M., editor). Dunod: Paris.
Doss, B. (1891) Der Meteorit von Misshof in Kurland. IN Arbeiten des Naturforscher-Vereins zu Riga (7):1-68.
Farrington, O. C. (1915) Meteorites: Their Structure, Composition, and Terrestrial Relations. The Lakeside Press, R. R. Donnelley & Sons Company: Chicago.
Prior, G.T. (1916) On the remarkable similarity in chemical and mineralogical composition of meteoritic stones: Mineralogical Magazine 17 (78):38. (April 1916).
Merrill, G.P. (1916) Handbook and Descriptive Catalogue of the Meteorite Collections in the U.S. National Museum. Bull. U. S. Natl. Museum, No.94, Washington. 207 pp., 41 pls.
Prior, G.T. (1923) Catalogue of Meteorites: with special reference to those represented in the collection of the British Museum of Natural History. Richard Clay & Sons, Limited: Bungay, Suffolk.
Mason, B. (1962) The Classification of Chondritic Meteorites. American Museum Novitates, No.2085. New York. 20 pp.
Mason, B. (1963) Olivine Composition in chondrites. Geochimica et Cosmochimica Acta 27: 1011-1023.
Yudin, I.A. (1970) Microscopic study of the Buschhof stony meteorite: Meteoritika, Vyp. (No.) 30, p. 88 - 92. (In Russian).
Graham, A.L., Bevan, A.W.R. & Hutchison, B. (1985) Catalogue of Meteorites (4/e). University of Arizona Press: Tucson.
Ramdohr. P. (1973) The Opaque Minerals in Stony Meteorites. Elsevier Publishing Company: Amsterdam; London: New York. 245 pages.
Rubin, A. E., Peterson, E., Keil,K., Rehfeldt, A. & Jarosewich, E. (1983) Fragmental breccias and the collisional evolution of ordinary chondrite parent bodies: Meteoritics 18(3): 179-196. (30 Sept 1983).
Alexeev, V. A. (1988) Parent bodies of L and H chondrites: Times of catastrophic events. Meteoritics & Planetary Science 33 (1): 145-152. (March 1988).
Emsley, J. (1998) The Elements (3/e). Clarendon Press: Oxford. 294 pages.
Grady, M.M. (2000). Catalogue of Meteorites (5/e). Cambridge University Press: Cambridge; New York; Oakleigh; Madrid; Cape Town. 689 pages.
Hutchison, R. (2004) Meteorites: A Petrologic, Chemical and Isotopic Synthesis. Cambridge University Press: Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo. 506 Pages.
Sears, D.W.G. ( 2004) The Origin of Chondrules and Chondrites: Cambridge Planetary Science Series, University of Cambridge Press: Cambridge,UK. 209 pages.
Guignard, J. & Toplis, M. J. (2015) Textural properties of iron-rich phases in H ordinary chondrites and quantitative links to the degree of thermal metamorphism: Geochimica et Cosmochimica Acta 149: 46-63. (Jan 2015).
Grady, M.M., Pratesi, G. & Moggi-Cecchi, V. (2015) Atlas of Meteorites. Cambridge University Press: Cambridge, United Kingdom. 373 pages.
End of Temporal Biblio
Historical, Linguistic, and Disciplinary Problematics of Mineralogical Reconstruction
Abstract
An extended discussion of the individual mineralites (minerals, mineral groupings, and sundry mineralogically phases ['items']) observed and recorded in 4 Latvian ordinary chondrite falls of the 19th Century is presented. 20 mineralites are discussed under four standard geochemical headings (silicates, Fe-Ni metal, sulfides, and oxides). A summary of the circumstances of these 4 witnessed falls, and a brief discussion of the problematics of reliably translating older observations into the proper contemporary terminology precede the core discussion. A selective bibliography is appended. While a primary focus of the text are some epistemological and linguistic issues associated with descriptions and classification, in-text links in the Table of Contents are provided for those interested in mineralogical specifics. Two small tables and one major table (Table C) included.
Table A: 4 Latvian Chondrites — Fall Phenomena | ||||||||||||||||||||||||||||||
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Notes:
'Municipality' - Latvia is currently organized into municipalities.
'Institution' — Location of university or academy housing the largest remaining mass. Additional info at MinDat location sites or the Catalogue of Meteorites (5/e).
Lixna mass - The 5.21 kg mass of Lixna listed with the Meteoritical Bulletin Database is the mass remaining after World War II. The larger original mass listed here appears both in the earliest reports and in several editions of the Catalogue of Meteorites, up to and including the 5th edition of 2000.
TABLE OF CONTENTS
- Introduction
- Problematics of Reconstruction: Linguistic, Historical, Disciplinary
- Preliminary Mineralogical Expectations
- Table C. Mineralites observed and recorded in 4 Latvian Ordinary Chondrites
- The Mineralite Inventory: Silicates, Fe-Ni metal, sulfides, and oxides
- Geochemical cohorts — I: Silicates (olivine, pyroxene, plagioclase…)
- Geochemical cohorts — II: Fe-Ni metal and other metals or alloys (siderophiles)
- Geochemical cohorts — III: Sulfides (esp. troilite) and phosphides
- Geochemical Cohorts — IV: Oxides
- Summary
- Footnotes
- Bibliography: Latvian Meteorites
Introduction
During the nineteenth century, the falls of four separate meteorites were observed and recorded in the small region of what is now the independent country of Latvia. No additional meteorite falls have been recorded in Latvia since that time. The timing and places of these four falls may strike us as a little odd, but statistical anomalies are frequently either merely statistical and/or undecipherable. What is more significance for science is that these falls were not only witnessed, but that significant portions of each meteorite have been preserved. Indeed, small samples are still occasionally used for current research (normally, however, only as one or data points on a long list). Even more important for both historical and scientific purposes, they were studied by scientists at some of the important museums and laboratories of the day during the century when the disciplines of chemistry, geology, physics and mineralogy were slowly emerging as separate discipline. For our purposes, it is important to note that the falls of these 4 meteorites occurred before X-rays were used to identify the unique atomic number of each element and the crystal structure of any sufficiently large mineral sample. These two developments, of course, are part of the assumed background for any contemporary discussion of either minerals or meteorites. For the past two years the author has been engaged in an effort to construct reasonably complete mineralogical inventories of scientifically and/or otherwise important meteorites and then post those findings in a publicly accessible venue (e.g.,'mindat.org'). There are, however, several factors that make the construction of such a mineral inventory a non-trivial task. What I wish to do here is state briefly some of the general problematics of my inquiry and then turn to the specifics of reconstructing the mineralogy of these four meteorites. I will then provide a critical assessment of both what has been accomplished and what still needs to be done.
TABLE B - QUICK MINERALOGICAL PROFILES FOR 4 LATVIAN CHONDRITES
Table B: 4 Latvian Chondrites — Individual Mineral Overview | ||||||||||||||||||||||||||||||
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M(N) is the composite tally for all MinDat recognized mineralites (or, 'items') [M] and IMA minerals [N], respectively.
A complete list w. citations for each meteorite is found at the individual meteorite's location site.
Problematics of Reconstruction: Linguistic, Historical, Disciplinary
The intention here has been to provide a mineralogical profile listing those minerals and other mineralogically important constituents which have actually been observed in specific meteorites. By 'observed' we mean that the observation has been referenced by a suitable source. By 'minerals and other mineralogically important constituents', we mean both those minerals and mineralogical groups which have been accepted as such by the International Mineralogical Associations (IMA defined phases) and any other variety, chemically defined phase, or mineralogically significant item which is accepted by 'mindat.org' (MinDat) as a listable mineralogical 'item'. The first problem with the protocol used here is that, as a general rule, an author who reports his/her findings about any meteorite does not necessarily list all minerals which were observed in the meteorite. Specifically, an author may not report mineral phases which are normally present, but not relevant to the topic pursued. These general problematics are, however, amplified in several important ways in our particular inquiry into mineralogical composition of the four 19th Century Latvian meteorites. Most fundamentally, the terminology for classifying and describing both meteorites and minerals has undergone significant changes during the past two centuries. Frequently, today's observer uses different words to describe a mineralogical phase identical to the phase observed by the original observer. In some cases a mineral may have been observed which was not recognized as a distinct mineral at the time (troilite is a pertinent example). We can sometimes determine that a currently recognized mineral was originally observed and described using pre-discovery terminology — but in these cases we must proceed carefully. Another underlying issue is that geochemical issues sometimes blunt mineralogical specificity in contemporary meteorite research. For example, mixed chemical-mineralogical terms (e.g., Ca-poor pyroxene) or bare chemical descriptors (e.g., silica, sulfide, silicon carbide) are simply unacceptable in many formal mineralogical venues including — at times — even MinDat with its more latitudinarian protocols. Such terms, however, are both ubiquitous and standard in contemporary meteorite research with its frequent dominantly geochemical focus. With these considerations in mind let us turn to some considerations of our four ordinary chondrites as a whole and then turn to the specific mineralogical phases which are present in one or more of the four 4 meteorites.
Classification of all meteorites are in actuality determined by an assemble of chemical, isotopic, textural, and mineralogical criteria which have developed over time. For our purposes we wish to express succinctly the relationship between the contemporary formalism as expressed at The Meteoritical Society's 'Meteoritical Bulletin Database' website and the mineralogical expectations for the ordinary chondrites considered here. All meteorites are unique (idiosyncratic) to some degree and there are always debates and revisions concerning the proper limits of every meteorite class, type or subtype. Some simplifying features for our four meteorites are that (1) as H- and L-chondrites they fit neatly into the norm of two of the most stable classification categories utilized by meteoriticists. These four meteorites are neither 'anomalous' nor 'borderline' H or L chondrites. (2) They are all witnessed falls and essentially 'unweathered'. And, finally, (3) their masses were sufficiently large as to minimize some of the inherent sampling problems encountered with very small samples (all chondrites are inhomogeneous at the smallest scales). Ordinary chondrites are formally defined by bulk elemental ratios, oxygen isotope ratios, and some subordinate textural/mineralogical criteria — items consistent with their original formation on small asteroidal bodies and their near solar-like chemistry for their non-volatile constituents. We focus here, however, on their expected mineralogical characteristics.[1]
Preliminary Mineralogical Expectations
We assume here that any sufficiently large and unweathered and properly classified ordinary chondrite contains olivine, pyroxene, and Fe-Ni metal. To be sure, we can also add that we would almost always expect to find troilite, small amounts of plagioclase and/or glass of plagioclase composition, and accessory chromite. Minor phosphates are usually to be expected as well. There is nothing particularly new here. The distinguishing mineralogical features of ordinary chondrites were succinctly summarized by Brian Mason several decades ago in one of his many American Museum Novitates (Mason, 1962)[2]. Our concern here is of a different nature. We are trying to establish a protocol to identify those mineralogical phases (mineralites) which have been specifically observed and, in some sense, recorded. We are not trying to identify those mineralites that are highly likely to be present or, even, almost certainly present. We will start by assuming that any unweathered meteorite which has been properly classified as an ordinary chondrite contains olivine and pyroxene. Others might wish to assume that, say, all properly classified H chondrites contain kamacite and that all petrologic type 6 H and L chondrites contain orthopyroxene. Perhaps. I think the case for assuming that all H6 and L6 chondrites contain orthopyroxene seems almost implied by definition. However, the observations are not really reported with that much mineralogical specificity. And, there is an advantage in waiting for more specific mineralogical reports. Detailed examination often reveals that our 'expected phases' are frequently accompanied by some unexpected phases.
There is an even more important reason for caution. Ordinary chondrites have normally experienced one or more serious shocks while in space and during their atmospheric entries. These shocks sometimes introduce significant mineralogical changes — transforming some phases into other phases. These shocks may effect the petrological type of a meteorite but they would not normally effect the meteorite's identity as a member of a defined chemical group (in this case, H or L-chondrite). And, our inventory is especially dependent upon the observer's equipment and skills. The presence of phases such as ilmenite, copper, and isocubanite in the mineral lists for Buschhof and Lixna is due to the fact that the eminent Paul Ramdohr investigated these meteorites with a petrographic refractor. Other instruments - such as the otherwise eminently useful microprobe - are not as helpful in uncovering the presence of these particular species unless the researcher targets such phases and has special skills. Before parsing our inventory, we note that because all the Latvian ordinary chondrites are of petrologic types 4-6, we begin with the fact that all of these meteorites have equilibrated or almost entirely equilibrated olivine. Secondly, the Fe-Ni metal in L chondrites is more Ni-rich than the Fe-Ni metal in H chondrites. Thus, a priori, one would expect taenite to be more readily observed in L- chondrites than in H-chondrites (all else being equal). Finally, we note here that three of the Latvian meteorites are described as veined in the latest edition of the Catalogue of Meteorites (5/e)[Grady, 2000]. The veins are normally due to pre-terrestrial shocks (or, occasionally, to fractures during atmospheric entry). Shocks also create glass and crystal twinning which may persist until eventually meteorite recovery. Thus we will start by assuming that olivine and pyroxene are present and consider all other mineralites on a case-by-case basis.[3]
Table C. Mineralites observed and recorded in 4 Latvian Ordinary Chondrites
These are the specific minerals and mineralogically significant items of our discussion. By definition the 10 International Mineral Association (IMA) minerals do not overlap with each other. However, other inclusive and overlapping categories such as mineral groups and series may be redundant in particular instances. Please note, also, that 'Fe-Ni metal' — the currently preferred term in most meteoritics literature — is not a MinDat category. Vide infra!
Table C: 20 Reported Minerals & Mineralites in 4 Latvian Chondrites
Minerals, Mineral Groups,Mineral Subgroups,Mineral Series,Mineral Varieties, Chemically Defined Aggregates, Glass
Table C: 20 Minerals & Mineralites in 4 Latvian Chondrites | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Mineralite&Host#= Mineral/Mineralite (with number of meteorite hosts in parenthesis)
TERMINOLOGY
Olivine and Plagioclase are 'Solid solutions series'
Pyroxene is a 'Mineral Group' with 'Subgroups' Orthopyroxene and Clinopyroxene.
'Diallage' is a variety of Diopside.
Plagioclase is treated as an exact synonym for the "Albite-Anorthite Series" by MinDat algorithms.
The Mineralite Inventory: Silicates, Fe-Ni metal, sulfides, and oxides
Actually, (1) Silicates, (2) Fe-Ni metal and other free elements, (3) sulfides-and-phosphides, and (4) oxides as we combine some of the minor categories.We proceed along lines of standard geochemical categories and then, roughly, by number of meteorite hosts. We say, roughly, because overlapping categories used in describing mineralites need to be disentangled as we proceed. As a preliminary note, we note the observed occurrences of olivine, pyroxene, plagioclase, Fe-Ni metal, troilite, and chromite in all 4 Latvian chondrites. We have listed these 6 mineralites, roughly, in order of volume abundance. The relative proportions of Fe-Ni metal and troilite, in particular, are not constant.
Geochemical cohorts — I: Silicates (olivine, pyroxene, plagioclase…)
Tally of Silicates Observed in Latvian MeteoritesOlivine reported in all 4 meteorites.
Pyroxene reported in all 4 meteorites.
Orthopyroxene (2) reported in Misshof and Lixna.
Clinopyroxene (2) reported in Misshof and Lixna.
Plagioclase reported in all 4 meteorites.
Glass is reported only in Misshof.
OLIVINE
Olivine is usually the most abundant mineral in ordinary chondrites. The olivine is prominent in both chondrules and in the more comminuted in matrix. Indeed, for decades meteorites which are now labelled as H and L chondrites were called 'Olivine-bronzite' and 'Olivine-hypersthene' chondrites, respectively. As a procedural matter, since exhaustive mineralogical observations have not always been explicit reported in Meteoritical Bulletins and in the various versions of the Catalogue of Meteorites, this author assumes as a procedural protocol that olivine has been observed in any meteorite which has been classified as either an 'Olivine-bronzite' or 'Olivine-hypersthene' chondrite in any edition of the Catalogue of Meteorites complied by the Natural History Museum (London) editors. In this case, the classification information is actually redundant since Brian Mason reported the composition of all 4 Latvian meteorites in 1962. In addition, his observations also indicated that the olivine in each of the meteorites is equilibrated.
PYROXENE
Pyroxene is always an abundant component in ordinary chondrites in both chondrules and matrix. The H and L chondrites were previously called 'Olivine-bronzite' and 'Olivine-hypersthene' chondrites. In most cases the dominant pyroxene is Ca-poor orthopyroxene, but there are exceptions. The primary complicating factor is that quickly cooled and/or shocked pyroxene may be partially or predominantly clinopyroxene. Again, as a procedural matter, this author assumes as a procedural protocol that pyroxene has been observed in any meteorite which has been classified as either an 'Olivine-bronzite' or 'Olivine-hypersthene' chondrite in any edition of the Catalogue of Meteorites. If the meteorite has not been seriously altered by shock, we could usually assume that almost all of the pyroxene in a petrologic type 6 ordinary chondrite is almost entirely orthopyroxene. However, the author normally requires a specific reference. A minor constituent in many ordinary chondrites are the two Ca-rich clinopyroxenes, augite and diopside.
Two problematics are relevant to our inquiry. It is only around the end of the 19th Century that consistent differentiation between augite or diopside as presently understood and other clinopyroxenes could be made on a consistent basis. Thus, for example, the "schwarzen Augit" [black augite] reported in Lixna by Kuhlberg (1865) is evidently 'clinopyroxene' and is so listed. However, it is unclear to this author whether the actual IMA defined species was pigeonite, diopside or augite. See Farrington (1915) for additional insight into the development of 19th Century pryoxene understanding. Developments of the last few decades have also altered the reporting of pyroxene mineralogy within the meteoritical literature. While the Latvian meteorites have not been scrutinized in great detail in recent decades, what current interest there is may be reported in geochemically focused venues which often suppress explicit attention to mineralogical detail. Current reports routinely note the presence of 'Ca-rich pyroxene' , but the actual per se detection of augite and/or diopside and/or pigeonite is not always a matter of interest. In many of these cases it is actually difficult to imagine that we are dealing with anything besides a 'clinopyroxene' — most likely diopside or augite (with hedenbergite an outside possibility).
Orthopyroxene is clearly present in both Lixna (H4)and Misshof (H5). We would expect that the two H6 chondrites Buschhof and Nerft would also have orthopyroxene, but unambiguous evidence is lacking. Clinopyroxene is also present in Misshof as diallage, a variety of diopside, and in Lixna.
PLAGIOCLASE
Plagioclase ('Albite-Anorthite Series' @MinDat) is a normal accessory component of almost all ordinary chondrites in both chondrules and matrix. And, indeed, plagioclase has been reported for all 4 Latvian chondrites so the general picture seems to be more or less as expected. We mention two minor complications which are not resolved here. Most ordinary chondrites have been at least mildly shocked on several occasions between original aggregation on the original parent body (OPB) and their eventual impact with the earth. Plagioclase is more easily converted to glass than either pyroxene or olivine so that some residual glass of plagioclase composition ('maskelynite') is usually present to some extent in ordinary chondrites. For type 4-6 chondrites most or all of the glass was devitrified by metamorphism on the OPB. The long journey between the OPB and the earth, however, created additional opportunities for the creation of glass.
GLASS
The apparent presence of glass in Misshof would presumably be due to late shock. Primary glass has been devitrified in Type 4-6 silicates, but secondary glass can be created by impact at any time. As three of the Latvian meteorites are described as 'veined' it is somewhat surprising that this author was able to find only one seemingly unmistakable reference for the glass. Perhaps someone with more knowledge of German and petrographic history can shed additional light on this subject.
SILICATE SUMMARY
As far as the principle silicates (olivine, pyroxene, and plagioclase), the outlines of our records are more or less as they should be. However, it is somewhat disappointing that more precise information about the intricate interplay between orthopyroxenes and clinopyroxenes is quite sparse.
TERMINOLOGY
We should also note that — while usage differs — there is a strong preference within many members of the meteoritical community to avoid the use of the term 'Feldspar' unless there is a strong potassium component within the usually Na- and or Ca- dominated mineral. On first impression it appear that most — if not all — of the 'Feldspar' reported here was in fact K-poor — i.e., 'Plagioclase' and thus we have listed it.
Geochemical cohorts — II: Fe-Ni metal and other metals or alloys (siderophiles)
Tally of Fe-Ni and other metalsFe-Ni Metal (or, 'Meteoritic Iron') is found in all 4 Latvian meteorites.
Kamacite (3) is specifically reported for Buschhof (L6), Lixna (H5), and Misshof (H5).
Taenite (2) is specifically reported for Buschhof (L6) and Misshof (H5).
Copper (2) is reported for Buschhof (L6) and Lixna (H5).
In most early reports of Fe-Ni metal in ordinary chondrites, the presence of unoxidized or 'free' Ni-bearing iron ['Nickeliferous iron'] became the recognized signature for almost all meteoritic materials as it clearly differentiated meteorites from any natural or terrestrial artificial heavy iron-ores and/or masses known at the time. Once the techniques of preparing polished surface became common, at least at research institutions, the use of a petrographic reflecting microscope enabled Reichenbach and others to differentiate between the merely Ni-bearing kamacite (Ni ~5-7%) and the Ni-rich taenite (Ni ~15-30%). X-ray crystallography later confirmed the mineralogical validity of the crystallographic distinction between the body-centered cubical kamacite and the face-centered taenite. It has now been known for over a century that most of the Fe-Ni metal found in ordinary chondrites has been partitioned into two phases. There are several second-order complications which we mention here, but they are — for the purposes of our current discussion which is restricted to 4 unweathered, moderate-sized ordinary 'ordinary chondrites' with equilibrated olivines— quite tractable. We have included elemental copper in our somewhat elastic geochemical grouping as it does not deserve a separate category.
Fe-Ni Metal
As our first consideration, then, we need to define some terms. 'Fe-Ni metal' is the current term of choice for the Ni-bearing iron invariably found in all iron-rich meteorites and in almost all chondritic meteorites. This Fe-Ni metal also contains cobalt (usually 0.3-1.0%) and lesser amounts of chromium and phosphorus. Now it should be understood that the term 'Fe-Ni' metal is not mineralogically neutral. As applied to ordinary chondrites, it contains the implicit understanding that in all likelihood — with some exceptions noted below — all or nearly all of the Fe-Ni metal is either kamacite and/or taenite. To be sure, minor amounts of other Fe-Ni metal phases have been reported from other ordinary chondrites — e.g., plessite and tetrataenite — but the author is unaware of such citations for the Latvian meteorites in the literature he has examined. For other meteorite classes, other considerations obtain. Thus, for example, in meteorites derived from the cores of larger, more slowly cooled parent bodies (irons, pallasites) and from highly shocked meteorites, other Fe-Ni rich metallic phases are sometimes found in significant quantities. But, these complications are not in evidence here.
The term 'Meteoritic Iron' used at MinDat is a close synonym for 'Fe-Ni metal' but it is a mineralogically neutral term. In the meteoritic literature, 'Fe-Ni metal' may be used because the author is not particularly concerned about explicit mineralogical terms and may not put in print what he or she has already observed. 'Meteoritic Iron' is actually a somewhat more positive label — at least as I read the term — as it normally means that the author has observed no convincing evidence for any definite Fe-, Ni-rich metallic phase. For example, stand alone microprobe observations often produce little (if any) per se mineralogical data.
KAMACITE & TAENITE
We can expand on what is known about kamacite and taenite in ordinary chondrites. As a first consideration, we note that the amount of Fe-Ni metal available for each of would be expected to variable. First, we discovered and have thus defined the two classes by the amount of total iron available — H (high-iron) ordinary chondrites and L (low-iron) ordinary chondrites. Secondly, within the two groups, there was some natural variability in original composition, in oxygen fugacity, sulfur abundances, and in cooling rates. However, thirdly, and most important for our discussion is that the oxygen fugacity for the L chondrites was significantly higher than for H chondrites. Subsequently, more iron preferentially entered the silicate phases (olivine and pyroxene) leaving the metallic phases more Ni-rich. Consequently, the fraction of taenite in L chondrite metal is actually higher than in H chondrites.
Thus, there is no surprise in the fact that some form of Fe-Ni metal has been reported for all 4 Latvian meteorites — either as kamacite and/or taenite or as 'meteoritic iron'. The simple 'meteoritic iron' reported for Nerft (L6), however, comes with some additional information. It is reported as consisting of 20% nickel. One suspects that the Fe-Ni metal is taenite. If so, then both L6 meteorites would contain taenite. Of course, the fact that taenite is reported for both one H5 fall and one L6 fall is not really too surprising.
Our overall inventory of Fe-Ni metal in the Latvian meteorites is thus somewhat as we might expect. However, much of this is due to the fact that, first, a great observer made an extensive study of the opaques in two of the meteorites and, secondly, a modern investigation by Guignard & Toplis (2015) has filled in some of the blanks for Misshof.
COPPER
The presence of copper in two Latvian meteorites is not surprising in itself. Copper is a ubiquitous, but very minor constituent in many ordinary chondrites. However, detecting copper is not a trivial observation. The two citation we have are both derived from Ramdohr's observation published just over 4 decades ago [Ramdohr, 1973]. Ramdohr was a maestro both of ore mineralogy and of reflected light microscopy. Today, in somewhat similar fashion, one notes the coincidental reports of meteorite copper in some of Alan Rubin's work — but one does not look for it in the average 'semi-complete' petrographic description.
Geochemical cohorts — III: Sulfides (esp. troilite) and phosphides
Tally of Sulfides and Phosphides in Latvian MeteoritesTroilite (4) — Troilite is reported for all 4 meteorite, usually by several observers.
Isocubanite (2) — Isocubanite (labelled 'Chalkopyrrhotite') was observed in Buschhof (L6) and Lixna (H4) by Ramdohr (1973).
Mackinawite (1) — Mackinawite was observed in Buschhof by Ramdohr (1973).
Schreibersite (2) — Schreibersite has been observed in both Lixna (H4) and Nerft (L6).
SULFIDE & PHOSPHIDE SUMMARY
Our reported inventory of sulfides and phosphides is certainly what we night expect from a brief foray into the mineralogical thicket of sulfides and phosphides. Both troilite and schreibersite were first discovered in meteorites and are ubiquitous components of many meteorite classes including — most notably — ordinary chondrites and irons. Sulfides are, of course, common in a number of terrestrial ores, but they tend to be turned into sulfates when they get close to the earth's more oxidizing crustal environment. Phosphides are extremely rare in terrestrial environments as terrestrial phosphorus is almost always found either as phosphate or as a, usually, minor component in various uncommon minerals. We would expect troilite to be present in any unweathered ordinary chondrite — and, indeed, we would be very surprised if troilite were not present in these 4 Latvian meteorites. The case for schreibersite is a little different. Schreibersite is commonly found in association with Fe-Ni metal and/or with troilite in ordinary chondrites, but is not always particularly abundant. There is, however, one complication that we must address directly. Troilite and schreibersite were first recognized as distinct minerals during the 19th Century. Thus, we will need to determine if whether pre-discovery observations of these phase were made before our current labels were used.
Pyrite had been used as a generic term for iron sulfides since the middle ages and only gradually became the specific term for one of our most common terrestrial iron sulfides. The cubic (isometric diploidal) crystal structure was obvious enough and the chemical parameters developed in due time. By the middle of the 19th Century pentlandite had been identified at Sudbury. Pentlandite is also isometric, but it tends to form massive aggregates and so its somewhat different crystal structure had not been so immediately obvious as that of pyrite. Its chemical affinity for Ni is also important as its enhanced Ni content differentiates pyrrhotite from the other iron sulfides we discuss here. In 1863 troilite was discovered in the Albareto chondrite. Troilite was clearly distinguishable both mineralogically (hexagonal) and chemically (stoichiometric FeS). Like pyrite, troilite is also non-magnetic. It gradually became clear that troilite was in fact the most common meteoritic iron sulfide. An additional complication arose, however, which effects our reading of the mineralogy of Latvian meteorites. Another hexagonal, but magnetic terrestrial iron sulfide was discovered also discovered about this time — pyrrhotite. It was sometimes referred to as 'magnetic pyrite' and, apparently, sometimes is still referred to by this term. In fact, however, we can also think of pyrrhotite as a hexagonal iron sulfide with an FeS1-x composition which 'becomes' non-magnetic troilite if x =0.
We must apply an important physical principle is in order to utilize our 19th Century records — oxygen fugacity (a measure of an elements 'activity' or, crudely, effective 'pressure'). While the abundance of sulfur is, of course, important, how iron interacts with sulfur is also quite dependent upon the activity of oxygen. When sufficient oxygen is available iron readily forms strong and stable Fe-O bonds and less iron is available to form sulfides. Of course, in many terrestrial environments almost all sulfur is found as sulfate. However, pyrite (FeS2) is the most common iron sulfide in many crustal environments. Pyrrhotite and pentlandite are also encountered in a number of moderately reduced terrestrial environments. During the early part of the 19th Century iron-sulfide in meteorites was almost invariably described as 'pyrite'. In 1863 it was determined that the iron sulfide in the Albareto chondrite was not pyrite. Troilite was clearly distinguishable mineralogically (hexagonal) and chemically (stoichiometric FeS). Troilite is also non-magnetic. Troilite has since been found in some very unusual terrestrial environments such as coal dumps as it is hexagonal Pyrite heretofore described 'pyrite crustal environments almost all sulfur is found as sulfate.
TROILITE
The case of troilite is mildly complicated but quite tractable. After is discovery in 1863, the term troilite gradually became standard, but adoption was sporadic. In 1884 Fremy referred to 'Pyrrhotine' in describing Nerft. In 1916 Merrill referred to 'Pyrrhotite' in describing Misshof. There is, however, no good reason to think that anything other than troilite is being described in these two meteorites. The German term "Magnetkies"— the current label for pyrrhotite — is also encountered with reference to troilite. With its shared hexagonal crystal symmetry and the chemical standards of the late 19th and early 20th it would have been either impossible or almost impossible to differentiate the two minerals. Etymologically, "Magnetkies" refers to pyrrhotite's weak magnetism. But demonstrating troilite's lack of a magnetic field in the presence of Fe-Ni metal a century or more ago is difficult to imagine in most circumstances. As long as we are discussing an unweathered, properly classified moderately equilibrated ordinary chondrite the dominant Fe-sulfide would always be troilite. Of course, a focused contemporary study of the micro-phases within the shock-melted veins of moderately or severely shocked ordinary chondrites could very well uncover some minor mineralogical deviations.
ISOCUBANITE
Ramdohr (1973) described isocubanite (synonym, isochalcopyrite) under the label 'Chalkopyrrhotite' in both Buschhof (L6) and Lixna (H4). Isocubanite is an isometric polymorph of cubanite which was formally recognized in 1988 by the IMA. It had apparently been recognized for a few decades as one of several phases or varieties of iron-copper sulfides found in certain terrestrial ores. While it is an invariably very minor constituent of stony meteorites, Ramdohr recognized its presence in nearly half of the 400 meteorites which he examined with a petrographic reflecting microscope.
MACKINAWITE
Ramdohr (1973) described mackinawite in Buschhof (L6) and Lixna (H4). Mackinawite is a tetragonal Fe-Ni sulfide formally recognized in 1962. While it appears to be an invariably very minor constituent of stony meteorites, Ramdohr recognized its presence in a significant number of stony meteorites. which he examined with a petrographic reflecting microscope. While it appears to be an invariably very minor constituent of stony meteorites, Ramdohr recognized its presence in over 90 stony meteorites of the roughly 400 meteorites which he examined with a petrographic reflecting microscope.
SCHREIBERSITE
Schreibersite is reported in both Lixna (H4) and Nerft ['Phosphornickeleisen' in Kuhlberg, 1865's description of Lixna]. This is not too surprising. Schreibersite is a common, but minor accessory in meteorites. As phosphorus is an order of magnitude more scarce in the solar system than sulfur we would not expect as a major role for phosphides. Even more importantly, phosphorus is more easily oxidized than sulfur. [Electronegativity of phosphorus is only 2.19 compared to Sulfur's 2.58, Cf. Emsley (1998),Elements (3/e)]. In fact, phosphates are frequently found even in iron meteorites where we would never expect to observe sulfates. In both older and newer meteoritical literature, there are frequent reports of phosphates or even Ca-phosphates — but these reports are mineralogically indeterminate. As a matter of fact — with, of course, some interesting exceptions — the great bulk of meteoritic phosphate minerals are almost always either apatite or merrillite (aka, whitlockite). Merrillite is essentially anhydrous whereas apatite normally carries a mixture of hydroxyl, chorine, and/or fluorine ions. For now we simply observe that — except when a special effort is made to find phosphates for, say, their radiogenic isotopes — both phosphide and phosphate minerals will be largely unnoticed and thus underreported in meteoritical studies of both old and more recent falls.
In a larger sample of thoroughly studied ordinary chondrites we, of course, find numerous additional instances of sulfides, carbides, and phosphides which are much rarer in oxidizing environments. However, as phosphorus is an order of magnitude more scarce in the solar system than sulfur we do not normally expect phosphides in great abundance in any ordinary chondrite.
Geochemical Cohorts — IV: Oxides
Tally of oxides in Latvian MeteoritesChromite (4) - Reported in all 4 Latvian meteorites, usually by more than one observer.
Ilmenite (1) - Reported in Lixna by Ramdohr (1973).
Oxides other than magnetite and chromite are not usually found in abundance in ordinary chondrites, but they are not necessarily rare. Ilmenite, rutile, spinel, and some silica polymorphs are occasionally reported. They may, however, require special lithological conditions and special observational attention before being reported. Silica polymorphs, for example, show up in quickly cooled inclusions which are out of equilibrium with the always abundant olivine. As no specific phosphates or carbonates have been noted in the reports cited here, we will forego any discussion of those phases. Likewise, it could very well be that the chromite reported here may have included instances of Ti-rich or Al-rich varieties which are not 'chromite' sensu strictu, but we will also forego that discussion.
CHROMITE
Chromite is the most common member of the spinel group to occur in ordinary chondrites. Thus it is not too surprising that it is reported for all four Latvian meteorites. It is, however, mildly surprising that magnetite has not been reported. Magnetite is both a ubiquitous component within the fusion crust of most meteorites and an occasional pre-terrestrial constituent of the original mineralogical assemblages of many chondrites.
ILMENITE
Ilmenite grains or exsolution lamellae in chromite are commonly found when time, proper equipment, and patience are present. The fact that its presence has not been reported for the other 3 meteorites besides Lixna does not mean that it is not present in one or more of them.
Summary
Combining observations made over the past two centuries we can reconstruct a reasonable outline of the primary mineral phases found in the 4 Latvian chondrites that fell in the 19th Century. The primary expected constituents — olivine, pyroxene, plagioclase, Fe-Ni metal, and troilite — have all been observed on one or more occasions (usually more than once) in all four of these ordinary chondrites. Accessory chromite was also found in all four meteorites. A few additional minor phases were found within one or more meteorite hosts (copper, isocubanite, mackinawite, Ilmenite, schreibersite). Most gratifying from a procedural perspective is that there appears to be no contradiction to our initial assumption that — for unweathered meteorites whose original parent bodies were, by terrestrial standards, environments of extremely low oxygen fugacity — we can successfully decode descriptions of troilite which were written before troilite had been recognized as a separate mineral.
There remain some outstanding issues. The Latvian pyroxene assemblages are almost certainly underreported. Pigeonite is not explicitly reported here in a single instance and diopside is only reported once. The descriptions of Fe-Ni metal also appear somewhat incomplete. While phosphorus is reported in some chemical assays, no specific phosphate minerals are reported here (schreibersite does appear twice). It may be that someone who has more complete access to the German literature (or is a more fluent reader than the author) could provide additional mineralogical information about the 4 meteorites. There could also be additional information about these meteorites in Slavic language venues (historical or modern) which this author is unable to understand. Perhaps some readers can make a contribution.
And in any case, we can always hope — and, when possible, insist — that a thorough report of a meteorite's mineralogical constituents are a necessary component of the information profile of any meteorite large enough to classify or important enough to study.
Footnotes
1. Hutchison, R. (2004) gives perhaps the most holistic treatment of meteorite classification during the past two decades. Sears (2004) provides elaborations on the relationships among pyroxene minerals within different petrologic types pertinent to our discussion.
2. Along with other changes, Mason's conclusions have been especially modified by the creation of an additional ordinary chondrite group (LL chondrites with very low bulk iron). Sears (2004) provides more current data on mineralogical variations related directly to petrologic types.
3. This normally comes either from a Catalogue of Meteorites or Meteoritical Bulletin report.
Bibliography: Latvian Meteorites
Meteoritical Bulletin Links; ABC BIBLIO; TIMEWISE BIBLIO:The Bibliography includes most major sources utilized in constructing the mineral lists for the 4 Latvian ordinary chondrite falls. It also provides several standard sources referred to in the text — particularly those which deal with the interplay between meteorite classification and mineralogy. The bibliography is provided into two frameworks — a standard alphabetical order for ease of use and a timewise order consistent with the fundamental historical approach of the article. A number of the older books are also available as free Google e-books. While there are a number of digital citations at the 4 individual Mindat location sites for the 4 meteorites, I have restricted my e-bibliography here to the minimum needed for quick access to the Meteoritical Bulletin Database which has immediate links to the SAO Astrophysical Data System and to Google. Most interested readers have their own procedures for accessing the World Wide Web and are usually more savvy than I.
E-Biblio Links to 'Meteoritical Bulletin Database
http://www.lpi.usra.edu/meteor/metbull.php - Meteoritical Bulletin Database
http://www.lpi.usra.edu/meteor/metbull.php?code=5178 -Buschhof@MetBullDatabase
http://www.lpi.usra.edu/meteor/metbull.php?code=14670 -Lixna@MetBullDatabase
http://www.lpi.usra.edu/meteor/metbull.php?code=16703 -Misshof@MetBullDatabase
http://www.lpi.usra.edu/meteor/metbull.php?code=16945 -Nerft@MetBullDatabase
BIBLIOGRAPHY ABC…
Alexeev, V. A. (1988) Parent bodies of L and H chondrites: Times of catastrophic events. Meteoritics & Planetary Science 33 (1): 145-152. (March 1988).
Doss, B. (1891) Der Meteorit von Misshof in Kurland. IN Arbeiten des Naturforscher-Vereins zu Riga (7):1-68.
Emsley, J. (1998) The Elements (3/e). Clarendon Press: Oxford. 294 pages.
Grady, M.M. (2000). Catalogue of Meteorites (5/e). Cambridge University Press: Cambridge; New York; Oakleigh; Madrid; Cape Town. 689 pages.
Grady, M.M., Pratesi, G. & Moggi-Cecchi, V. (2015) Atlas of Meteorites. Cambridge University Press: Cambridge, United Kingdom. 373 pages.
Graham, A. L., Bevan, A. W. R. & Hutchison, B. (1985) Catalogue of Meteorites (4/e). University of Arizona Press: Tucson.
Grewingk, C. & Schmidt, C. (1864) Ueber die Meteoritenfälle von Pillistfer, Buschhof und Igast in Liv-und Kurland. Heimrich Laakmann: Dorpat.
Guignard, J. & Toplis, M. J. (2015) Textural properties of iron-rich phases in H ordinary chondrites and quantitative links to the degree of thermal metamorphism: Geochimica et Cosmochimica Acta 149: 46-63. (Jan 2015).
Farrington, O. C. (1915) Meteorites: Their Structure, Composition, and Terrestrial Relations. The Lakeside Press, R. R. Donnelley & Sons Company: Chicago.
Hutchison, R. (2004) Meteorites: A Petrologic, Chemical and Isotopic Synthesis. Cambridge University Press: Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo. 506 Pages.
Kuhlberg, K. (1865) Analyse und Beschreibung der Meteorite von Nerft, Honolulu, Lixna und eines im Gouvernement Jekatherinoslaw gefallenen Meteoriten. Heimrich Laakmann: Dorpat.
Mason, B. (1962) The Classification of Chondritic Meteorites. American Museum Novitates, No.2085. New York, 1962, 20 pp.
Mason, B. (1963) Olivine Composition in chondrites. Geochimica et Cosmochimica Acta 27: 1011-1023.
Merrill, G. P. (1916) Handbook and Descriptive Catalogue of the Meteorite Collections in the U.S. National Museum. Bull. U. S. Natl. Museum, No.94, Washington. 207 pp., 41 pls.
Meunier, S. (1884) Météorites: In Encyclopédie chimique: Métalloïdes, vol II (Fremy, M., editor). Dunod: Paris.
Poggendorf, J.C. (1852) Annalen der Physik un Chemie. JA Barth: Leipzig.
Prior, G.T. (1916) On the remarkable similarity in chemical and mineralogical composition of meteoritic stones: Mineralogical Magazine 17 (78):38. (April 1916)
Prior, G.T. (1923) Catalogue of Meteorites: with special reference to those represented in the collection of the British Museum of Natural History. Richard Clay & Sons, Limited: Bungay, Suffolk.
Ramdohr. P. (1973) The Opaque Minerals in Stony Meteorites. Elsevier Publishing Company: Amsterdam; London: New York. 245 pages.
Rubin, A. E., Peterson, E., Keil, K., Rehfeldt, A. & Jarosewich, E. (1983) Fragmental breccias and the collisional evolution of ordinary chondrite parent bodies: Meteoritics 18(3): 179-196. (30 Sept 1983).
Yudin, I. A. (1970) Microscopic study of the Buschhof stony meteorite: Meteoritika, Vyp. (No.) 30, p. 88 - 92. (In Russian).
[End of ABC Bibliography]
BIBLIOGRAPHY (Temporal Order)
Poggendorf, J.C. (1852) Annalen der Physik un Chemie. JA Barth: Leipzig.
Grewingk, C. & Schmidt, C. (1864) Ueber die Meteoritenfälle von Pillistfer, Buschhof und Igast in Liv-und Kurland. Heimrich Laakmann: Dorpat.
Kuhlberg, K. (1865) Analyse und Beschreibung der Meteorite von Nerft, Honolulu, Lixna und eines im Gouvernement Jekatherinoslaw gefallenen Meteoriten. Heimrich Laakmann: Dorpat.
Meunier, S. (1884) Météorites: In Encyclopédie chimique: Métalloïdes, vol II (Fremy, M., editor). Dunod: Paris.
Doss, B. (1891) Der Meteorit von Misshof in Kurland. IN Arbeiten des Naturforscher-Vereins zu Riga (7):1-68.
Farrington, O. C. (1915) Meteorites: Their Structure, Composition, and Terrestrial Relations. The Lakeside Press, R. R. Donnelley & Sons Company: Chicago.
Prior, G.T. (1916) On the remarkable similarity in chemical and mineralogical composition of meteoritic stones: Mineralogical Magazine 17 (78):38. (April 1916).
Merrill, G.P. (1916) Handbook and Descriptive Catalogue of the Meteorite Collections in the U.S. National Museum. Bull. U. S. Natl. Museum, No.94, Washington. 207 pp., 41 pls.
Prior, G.T. (1923) Catalogue of Meteorites: with special reference to those represented in the collection of the British Museum of Natural History. Richard Clay & Sons, Limited: Bungay, Suffolk.
Mason, B. (1962) The Classification of Chondritic Meteorites. American Museum Novitates, No.2085. New York. 20 pp.
Mason, B. (1963) Olivine Composition in chondrites. Geochimica et Cosmochimica Acta 27: 1011-1023.
Yudin, I.A. (1970) Microscopic study of the Buschhof stony meteorite: Meteoritika, Vyp. (No.) 30, p. 88 - 92. (In Russian).
Graham, A.L., Bevan, A.W.R. & Hutchison, B. (1985) Catalogue of Meteorites (4/e). University of Arizona Press: Tucson.
Ramdohr. P. (1973) The Opaque Minerals in Stony Meteorites. Elsevier Publishing Company: Amsterdam; London: New York. 245 pages.
Rubin, A. E., Peterson, E., Keil,K., Rehfeldt, A. & Jarosewich, E. (1983) Fragmental breccias and the collisional evolution of ordinary chondrite parent bodies: Meteoritics 18(3): 179-196. (30 Sept 1983).
Alexeev, V. A. (1988) Parent bodies of L and H chondrites: Times of catastrophic events. Meteoritics & Planetary Science 33 (1): 145-152. (March 1988).
Emsley, J. (1998) The Elements (3/e). Clarendon Press: Oxford. 294 pages.
Grady, M.M. (2000). Catalogue of Meteorites (5/e). Cambridge University Press: Cambridge; New York; Oakleigh; Madrid; Cape Town. 689 pages.
Hutchison, R. (2004) Meteorites: A Petrologic, Chemical and Isotopic Synthesis. Cambridge University Press: Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo. 506 Pages.
Sears, D.W.G. ( 2004) The Origin of Chondrules and Chondrites: Cambridge Planetary Science Series, University of Cambridge Press: Cambridge,UK. 209 pages.
Guignard, J. & Toplis, M. J. (2015) Textural properties of iron-rich phases in H ordinary chondrites and quantitative links to the degree of thermal metamorphism: Geochimica et Cosmochimica Acta 149: 46-63. (Jan 2015).
Grady, M.M., Pratesi, G. & Moggi-Cecchi, V. (2015) Atlas of Meteorites. Cambridge University Press: Cambridge, United Kingdom. 373 pages.
End of Temporal Biblio
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Quick NavIntroductionProblematics of Reconstruction: Linguistic, Historical, DisciplinaryPreliminary Mineralogical Expectations Table C. Mineralites observed and recorded in 4 Latvian Ordinary ChondritesThe Mineralite Inventory: Silicates, Fe-Ni metal, sulfides, and oxidesGeochemical cohorts — I: Silicates (olivine, pyroxene, plagioclase…)Geochemical cohorts — II: Fe-Ni metal and other metals or alloys (siderophiles)Geochemical cohorts — III: Sulfides (esp. troilite) and phosphidesGeochemical Cohorts — IV: OxidesSummaryFootnotesBibliography: Latvian Meteorites
