Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsThe Rock H. Currier Digital LibraryGeologic Time
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsClubs & OrganizationsMineral Shows & EventsThe Mindat DirectoryDevice SettingsThe Mineral Quiz
Photo SearchPhoto GalleriesSearch by ColorNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryPhotography
╳Discussions
💬 Home🔎 Search📅 LatestGroups
EducationOpen discussion area.Fakes & FraudsOpen discussion area.Field CollectingOpen discussion area.FossilsOpen discussion area.Gems and GemologyOpen discussion area.GeneralOpen discussion area.How to ContributeOpen discussion area.Identity HelpOpen discussion area.Improving Mindat.orgOpen discussion area.LocalitiesOpen discussion area.Lost and Stolen SpecimensOpen discussion area.MarketplaceOpen discussion area.MeteoritesOpen discussion area.Mindat ProductsOpen discussion area.Mineral ExchangesOpen discussion area.Mineral PhotographyOpen discussion area.Mineral ShowsOpen discussion area.Mineralogical ClassificationOpen discussion area.Mineralogy CourseOpen discussion area.MineralsOpen discussion area.Minerals and MuseumsOpen discussion area.PhotosOpen discussion area.Techniques for CollectorsOpen discussion area.The Rock H. Currier Digital LibraryOpen discussion area.UV MineralsOpen discussion area.Recent Images in Discussions
Improving Mindat.orgMisuse of term "Pseudomorph"
16th Aug 2011 12:19 UTCJolyon Ralph Founder
In order to be consistent, this is a simplified guide as to what is, or is not, a pseudomorph:
When one mineral, fossil or structure is replaced with a new mineral, it is in general called a REPLACEMENT.
When this replacement mimics the crystal form of the original mineral by taking over the space occupied by the previous crystal, the term pseudomorph is used.
If something is replacing a fossil, or a piece of wood, or a worm tube, or any other non-crystalline structure, then it is a REPLACEMENT, not a pseudomorph.
If something replaces a crystal of a previous mineral, then it is a pseudomorph. But, to be a pseudomorph the crystal form of the original mineral has to be visible in the new specimen. If the original mineral was an anhedral grain, then it's not a pseudomorph. If the new mineral has overgrown and replaced the original mineral to such an extent that no measurable or visible signs of the original crystal shape can be detected, then it's a replacement not a pseudomorph.
If something is the remains of a coating that was previously coating a now missing mineral, then it is an epimorph, not a pseudomorph.
if something has changed at the crystal structure level only, and there is no chemical change (for example, aragonite converting to calcite, but retaining the original shape of the aragonite crystal) then it is a paramorph - a special class of pseudomorph (so both terms are correct in this case, but paramorph is preferred).
If in doubt, use the term 'replacement' instead of 'pseudomorph'.
Thanks!
Jolyon
ps. This document is a work in progress. Please comment below if you think things could be explained better, or if you think anything is incorrect
16th Aug 2011 13:43 UTCEvan Johnson
Maybe I'm reading too deeply into this, or maybe it's my lack of understanding, but this seems like it might not necessarily be true. If we are to assume that an anhedral grain can be a mineral (and I think that most would agree with that), and we partially (or completely, if demonstrable) replace it with another mineral, isn't it still a (not particularly attractive) pseudomorph? That is to say, we're replacing one lattice and composition with another- on an atomic scale, wouldn't euhedral and anhedral replacements appear similar? So, there is temporal but not spatial variance, with one accepted mineral species replacing another accepted mineral species. Actually, maybe that last sentence would summarise my view of pseudomorphism in general. Hope I'm not splitting hairs too far.
Cheers,
EMJ
16th Aug 2011 13:56 UTCAntonio Borrelli Expert
From the following link I found a good description for the usage of this term:
http://www.mineralsocal.org/bulletin/2005/2005_jan.htm :
"5. Perimorph: Not to be confused with paramorph. A perimorph is a special type of pseudomorph which is formed when one mineral is encrusted by another, and then the original mineral is leached out leaving a hollow shell in the form of the original mineral. Epimorphs are a special case of a perimorph. L.P. Gratacap in his Popular Guide to Minerals (1912, 63) defines an epimorph as “a pseudomorph formed by encrustation as when quartz coats calcite, concealing the covered mineral completely though assuming the crystalline form of the calcite. Such phases of pseudomorphism are called epimorphs."
16th Aug 2011 14:44 UTCJolyon Ralph Founder
> isn't it still a (not particularly attractive) pseudomorph?
No, it's a replacement!
A pseudomorph HAS to be something that has a deceptive form taken after the crystallography of another mineral species.
If this form is not there, it's not a pseudomorph.
We tend to be forgetting that the word 'pseudomorph' means something very specific. A false (or deceptive) form. Out of laziness people have started using it for a mineral replacement of anything.
But not any more. Not on my website. We do things properly from now on :)
Jolyon
16th Aug 2011 14:45 UTCJolyon Ralph Founder
16th Aug 2011 15:12 UTCAntonio Borrelli Expert
But with my poor comprehension of the English language, in the description I pasted above I understand that in the past an epimorph of mineral X on mineral Y may not implied the leaching out of mineral Y. It was considered an overgrowth encrustation.
If you are thinking to edit a new page for 'pseudomorphs' or some sticky note at the top of some uploading form maybe this information should be added.
16th Aug 2011 15:39 UTCAlfredo Petrov Manager
We could simplify this issue by abandoning the word "pseudomorph" altogether and just lump all these phenomena together under the title "Replacements", which no one could quibble with.
16th Aug 2011 16:12 UTCJolyon Ralph Founder
Jolyon
16th Aug 2011 16:38 UTCEvan Johnson
I really don't mean to be annoying or pedantic about it, but something still strikes me as intuitively wrong about when I drop or damage a malachite after azurite, breaking it (an experiment, with n=several that I have regrettably performed), it changes from a pseudomorph to a replacement- similarly with something damaged in a mining operation, or affected by weathering, or light. I fully understand "pseudo-" and "-morph," but to me it's like claiming something isn't crystalline simply by virtue of the fact that it does not show faces. That said, I of course accept your definition, and will let the issue go.
Regards,
EMJ
16th Aug 2011 17:07 UTCUwe Kolitsch Manager
It would be interesting to compare the definition of pseudomorph etc. in several standard English and non-English mineralogy textbooks.
16th Aug 2011 18:22 UTCJolyon Ralph Founder
This is the clear distinction to me between a replacement (the malachite in this case is still a replacement of original azurite) and pseudomorph, which is a term to describe a visible relationship between the new mineral and the mineral it replaced.
As for where to draw the line - if measurable or visible signs of the original crystal shape can be detected then the term pseudomorph is approprite. If not, then it's just a replacement.
To say the chunk of malachite in the example above is still a pseudomorph is as nonsensical as describing a faceted gemstone as anhedral or euhedral based on the original crystal shape before it was cut.
Uwe - it may be interesting to note about other uses of the word 'pseudomorph' by collectors and in mineralogy books worldwide, but the key thing here is to come to a standard definition that mindat.org will stick to internally.
16th Aug 2011 18:37 UTCEvan Johnson
Thanks for the explanation.
EMJ
16th Aug 2011 19:04 UTCRick Dalrymple Expert
Replacement; 1. Metasomatism. 2. A process of fossilization involving substitution of inorganic matter for the original organic constituents of a plant or animal.
Pseudomorph; A mineral whose outward crystal form is that of another mineral; it is described as being “after” the mineral whose outward form it has, e.g. quartz after fluorite.
Metasomatism; The process of practically simultaneous capillary solution and deposition by which a new mineral may grow in the body of and old mineral or mineral aggregate. The presence of interstitial, chemically active pore liquids or gases contained within the rock body or introduced from external sources are essential for the process, which often, though not necessarily, occur at the constant volume with little disturbance of the textual or structural features.
I realize there are other definitions that may be used and printed in other publications. But I think these give a good basis for understanding what the differences are between these terms.
The definition for pseudomorph is limited to non-fossils and euhedral crystals. I think most of us do use the term “pseudomorph” loosely and we should use the term replacement instead. This would sound better than saying “quartz metasomatic fluorite”
The definition for metasomatism insinuates that a visible recognition of a crystal replacement is possible but I would think that a microscopic grain or crystal could be replaced without a visible identification.
And massive mineral aggregates that are replaced with a new mineral without euhedral crystals visible would be called a replacement and not a pseudomorph.
These definitions would support Jolyon’s guidelines.
Now for the term “altered”. From the same dictionary;
Alteration; Changes in the chemical or mineralogical composition of a rock, generally produced by weathering or hydrothermal solutions.
This definition seems to be the act changing of one mineral to another. The dictionary doesn’t list the words as nouns, verbs, etc. But it seems to me this is a verb where “replacement” is a finished product (a noun).
Using these definitions, an azurite crystal changing to malachite is actually altering as long as the geo-processes are still in action. Once the specimen is removed from the ground the geo-processes are done and it is then a pseudomorph (at least as pseudomorphed as it is going to get).
16th Aug 2011 19:42 UTCAthanasios Ziros
Pseudomorphosis
Pseudo + morphosis derives from Greek Ψευδό + μόρφωσις
Pseudo means false in a deceptive way, fallacious
Morphosis means to take/give shape or pattern
Therefore concerning mineralogy the term is properly used when a mineral replaces another and you are initially tricked due to the crystal shape in wrong identification. The element of deceit is necessary.
No one is tricked with pyrite replacing an ammonite
You can however use from a grammatical point of view the term morphosis without pseudo to describe form i.e. Pyrite morphosis (morphene) after ammonite, meaning pyrite with the shape-form of an ammonite.
“Pseudomorphosis” has been widely used in theology, history and philosophy y since classical ages, mostly to describe heresy, controversial and false reciting of events, brainwashing, etc.
P.S.
perimorph περι + μορφη means all around includeed by + form
epimorph επι+ μορφη means on top,above + form
paramorph παρα + μορφη means altered shape due to tension (in non elastic mateials like metals)
Best regards,
Athanasios.
16th Aug 2011 22:27 UTCRock Currier Expert
Currently I have cast a wide umbrella to cover as many pseudomorph type things as I can. I would eventually like to tag each locality entry type with the name of its pseudomorph type. There will never be complete agreement about what is absolutely correct here, and in those areas where there is reasoned logical dissent I would like to also present opposing points of view.
16th Aug 2011 22:54 UTCNorman King 🌟 Expert
Crystallographic inversion occurs where one mineral replaces another, but there is no change in chemical composition, such as aragonite inverting to calcite. As far as I know, this term is still used. So, I conclude that polymorphs can invert one to another, creating a paramorph, such as calcite after aragonite. I have also seen fairly recent accounts of the mechanism of opal-CT inversion to quartz. Opal-CT displays the x-ray characteristics of tridymite and low cristobalite, so this phase of the opal to quartz transformation apparently occurs after water is lost. The opal-A to opal-CT transformation is the stage when water is lost. I realize there is some uncertainty as to just what opal-A is, or what the range of things is that might have been called “opal” (opal-A), but restricting the discussion to the opal-CT to quartz transformation should take care of that. Previous authors I have read make just that restriction in application of the term inversion, but I am no expert, myself.
Nevertheless, the term “inversion” might also be mentioned here.
16th Aug 2011 23:18 UTCJolyon Ralph Founder
>those areas where there is reasoned logical dissent I would like to also present opposing points of view.
This is what this thread is for. But once we have decided on a use of the terms we really must make sure we stick to them throughout the site, otherwise it just becomes a mess.
But here, this debate is very welcome.
17th Aug 2011 08:38 UTCEmanuele Rambaudi
A "looser" use of the word "pseudomorph" can also be seen in natural sciences, when speaking about those ink clouds that many cephalopods use to deceive predators, aiming to mimick the size and shape of the squid itself.
That said, if the term "replacement" may be more handy for classification issues here in Mindat, that's ok for me. :)-D
Last notes. As Antonio was saying some posts before: an epimorph occurs when a complete coating takes place; a perimorph occurs when a coating takes place and the coated mineral is no longer present (what you see is only a hollow shape). The use of these terms is neither so widespread nor of simple understanding, but they might be considered pseudomorph sub-categories and sometimes come in handy. P.S. The name of the author "Gratacap" quoted by Antonio resembles the italian "grattacapo", which means more or less "nuisance, trouble, headache". A coincidence? :)
Ciao,
Emanuele
17th Aug 2011 13:43 UTCRalph S Bottrill 🌟 Manager
The term pseudomorph (French = la pseudomorphose) was coined by René Just Haüy (1743-1822) in his epochal Traité de Mineralogie (1801, Vol. 1, 140). Haüy did not, however, use it in its present sense. As part of a general discussion about types of concretions he coined the term from the Greek pseudo (false) and morph (form) for mineral bodies that owed their outward form to circumstances other than their own unique powers of crystallization or formation. Most of the discussion was devoted to fossils, especially fossil shells and petrified wood. He also included at the end of the discussion, the comment “...bodies which have a false and deceitful figure” which “...present in a very remarkable manner foreign or strange forms which they have in some measure obtained from other bodies which had received them from nature (ibid.).” After considerable discussion of what we would now classify as fossils, he adds that, “The mineral kingdom also has its pseudomorphoses. We find some substances of this kingdom under crystalline forms which are only borrowed; and it is probable that, in some cases at least, the new substance has been substituted gradually for that which has ceded its place to it as we suppose takes place with respect to petrified wood (ibid.).”
Ref: http://www.mineralsocal.org/bulletin/2005/2005_jan.htm
Personally i feel it safer to use "replacement" or "overgrowth" unless the original crystal form is very clear. Too many "pseudomorphs" need a lot of imagination to see the original crystals, eg. http://www.mindat.org/photo-1014.html and many are better termed overgrowths, but the term obsesses many collectors.
Metasomatism is used more for rocks than minerals.
17th Aug 2011 13:55 UTCJolyon Ralph Founder
If you are a professional mineralogist, petrologist or palentologist, I'd be very interested to hear what you believe is the correct scientific usage of the term.
Also, if the term has been defined in any style or editorial guides for mineralogical or other earth sciences publications, again we should listen to what they say.
It's current scientific usage that is important, historical roots and usage, and what normal collectors use the term for are interesting, but a diversion.
Jolyon
17th Aug 2011 14:37 UTCEarl Verbeek Expert
1. "Infiltration pseudomorphs"- If crystals of one mineral (e.g., halite) encased in sediment or rock dissolve, and another mineral subsequently precipitates in the crystal-shaped voids, you have (to my mind at least) a valid pseudomorph. However, the later mineral simply filed a void -- it did not replace an earlier one.
2. Hydration-dehydration pseudomorphs- Tincalconite after borax is one example. I do not think of dehydration as a replacement process, but perhaps others do. And what about autunite from the Daybreak mine, which can be autunite one day but meta-autunite another, depending on relative humidity? Here there is no discernible change in external appearance at all.
3. "Radiation pseudomorphs"- If the lattice structure of a zircon crystal is destroyed by radioactive decay of thorium as an impurity element, thereby resulting in an amorphous (metamict) zirconium silicate "glass," is this not a special type of pseudomorph?
17th Aug 2011 17:33 UTCPeter Haas
17th Aug 2011 18:29 UTCRoger Lang Manager
Strunz, Hugo (1982): Pseudomorphosen - Der derzeitige Kenntnisstand. Versuch einer Klassifizierung. - Der Aufschluss, 33, pp 313-342.
It´s in german .. but maybe somebody has the time to translate ;-) .. i haven´t at the moment ...
cheers
Roger
18th Aug 2011 12:45 UTCEarl Verbeek Expert
18th Aug 2011 13:57 UTCRalph S Bottrill 🌟 Manager
(You can see why the collective noun for geologists is an "argument")!
18th Aug 2011 14:12 UTCJolyon Ralph Founder
18th Aug 2011 16:42 UTCChester S. Lemanski, Jr.
18th Aug 2011 16:43 UTCWilliam C. van Laer Expert
18th Aug 2011 19:41 UTCJohan Kjellman Expert
For you who read german - enjoy. For you who don't - maybe an evening class will make for a new richer life!!
cheers
http://books.google.com/books?id=YIwJAAAAIAAJ&printsec=frontcover&dq=intitle:pseudomorphosen+inauthor:blum&hl=sv&ei=0xkSToy2JMvusga9hsHiDg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCwQ6AEwAA#v=onepage&q&f=false
18th Aug 2011 21:42 UTCJim Robison
If I had access to my papers, I would turn to an article in Rocks and Minerals several years back when John Sampson White, I think, had several pages on the definition of a pseudomorph, etc. in an excellent article. (Perhaps someone on the forum can cite the article).
In addition, there is a real expert on this topic in California (actually a husband and wife pair). Si and Ann Frazier have spent many hours over the past decades studying, and writing about, pseudomorphs, starting with the Gratacap paper, and references well before that, and up to recent years. If I can, when I return, I'll scan Si's presentation to one of the California mineral society meetings and add it as a pdf file, after I get permission from the Frazier's to do that.
Jim
19th Aug 2011 05:31 UTCRock Currier Expert
Evolution of a Pseudomorph
The term “Pseudomorphoses” was coined by the French crystallographer, the Abbe Rene Just Hauy in 1801(Traite de Mineralogie, Vol 1, pp140-5) . In his study, he believed the pseudomorph to be a type of concreation, which displayed a ‘’False or Deceitful’’ form. They were to be created thru the infilling of a foreign material in the viod , once occupied by another object – MOLDS & CASTS. Most of his examples, dealt with preserving the shape of shells and woods. To him, a pseudomorph was more likely to represent a mineralized fossil, a concept often ignored today. He did state, however that similar things did occur in the Mineral Kingdom.
A MOLD represents the hollow impression, resulting from the removal of the original host from a more resistant matrix. The interior wall-zone now preserves the overall shape of the original material. From those impressions, the identity of the host may be identified. They have been called Solution Pseudomorphs or Negative Crystals.
Ex Quartz Mold after Glauberite, Upper New Street Quarry, NJ
Quartz Mold after Fluorite, Cumberland, England
A CAST results from the simple infilling of any new material in the hollow MOLD. This thus can create a replica after the original host. Now it helps if the CAST is of a more resistant material than the enclosing matrix, so they may weather out for study. Called by some; Infiltration Pseudomorphs.
Ex Quartz Cast after Glauberite, , Lower New Street Quarry, NJ
Opal Cast after Shell, Australia
Quartz Cast after Halite, Arizona
Another slightly different hybrid case, involves two different, free-formed minerals, growing side by side. As they increase in size, they may create a common Interface. With the removal of one of the pair, an impression of the vanished species may remain on the side of the remaining crystal. The Swiss call this partial MOLD, a “Narben”, meaning Scar.(Frazier 2005 MSSC).
19th Aug 2011 11:26 UTCJohan Kjellman Expert
Blum goes through the history of the pseudomorph concept, starting with Werner, Breithaupt, Haüy, Hausmann, Naumann, Haidinger and Landgrebe. Then he goes on discussing different types.
cheers
19th Aug 2011 12:59 UTCJolyon Ralph Founder
No-one doubts that when Hauy used the term 'pseudomorph' he was considering fossils as well as minerals, but then terms change over time. We no longer refer to red spinel as 'Ruby', but that was allowed with the original definition.
The debate has been going on for some time. By the 1860s we already had the same arguments as we're having here!
Mr James Plant read a paper "On the so called Pseudomorphous Crystals of Chloride of Sodium found in the Upper Triassic rocks of Leicestershire and the adjoining counties".
Mr Plant gave Bischof's definition of the term pseudomorphous stating that it is applied to such minerals as possess geometrical forms foreign to themselves and acquired in a way entirely different from crystallization They are divided into two classes first alterative pseudo morphs produced either by removal addition or exchange of constituents; second displacement pseudomorphs produced by incrustation or by replacement. But the pseudomorphs found in the Triassic rocks belong to neither of these classes they are produced by a deposition of substances in cavities left in rocks by the solution of imbedded crystals analogous to casting in a mould, thus though the outside of the cast assumes all the minute appearance of a crystal the inside possesses none of the properties of a true crystal having no cleavage planes axes etc.
19th Aug 2011 21:52 UTCRock Currier Expert
Yes, you are right. Kieth is not trying to revert us to Hauy's old definition, but to give us a sense feeling where the term pseudomorph came from and its original usage.
12th Oct 2016 15:47 UTCAlfred L. Ostrander
I am just kicking this thread up to the top of the heap, so to speak. Under the General category a thread has been running on pseudomorphs. Lots of great photos of minerals and a lot of things that may or may not be pseudomorphs. Maybe this discussion should continue to support the clarification of definitions Jolyon wants for usage on Mindat.
Best Regards,
Al O
12th Oct 2016 18:32 UTCSteve Hardinger 🌟 Expert
12th Oct 2016 20:30 UTCRolf Luetcke Expert
Your point is well taken and it was very nice to read the older thread Jolyon posted.
I have myself used the term "loosely" since it is a forum to show off "replacements" and I agree, I need to be more careful with the term.
I was hoping it was a place for people to share favorites and to a great extent it has been just as I had hoped.
As with mineral species and locations, one needs to be as accurate as possible and I have to say, I have learned a thing or two on the thread myself.
I appreciate peoples interest in what I think is a wonderful sub category of mineral collecting.
Rolf
12th Oct 2016 22:51 UTCAlfred L. Ostrander
The pictures have been great! Some just might not be pseudomorphs. That poses a question that is difficult to answer as the usage through time seems to have been clouded up a bit and much doesn't appear to be what the Abbe Rene Just Huay intended. Some the applications of the term through have been replaced by better terms with clearer definitions. I'm still sorting out some of those terms myself and don't mind asking for insight on clearer definitions. I did some great time at university studying things geologic. I have had a lot of years at this mineralogy thing and still want to keep on learning. I've got my index cards laid out for terms such as perimorph and paramorph, etc. and am getting the best definitions for each term that I can find. Maybe not what Sherlock intended but the game is afoot!
Best Regards,
Al O
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: April 24, 2024 21:06:23
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: April 24, 2024 21:06:23