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Tourmaline group

Posted by Rock Currier  
avatar Tourmaline group
May 03, 2012 11:13AM
Click here to view Best Minerals and here for Best Minerals tourmaline group minerals, here for Best Minerals chromium-dravite, here for chromo-alumino-povondraite, here for darellhenryite, here for dravite, here for elbaite, Afghanistan to Nigeria, here for elbaite, Pakistan to Zambia here for feruvite, here for fluor-buergerite here for fluor-dravite, here for fluor-elbaite, here for fluor-feruvite, here for fluor-liddicoatite, here for fluor-schorl, here for fluor-tsilaisite, here for fluor-uvite, here for foitite, here for liddicoatite, here for luinaite-(OH), here for magnesiofoitite, here for olenite, here for oxy-chromium-dravite, here for oxy-dravite, here for oxy-rossmanite, here for oxy-schorl, here for oxy-vanadium-dravite, here for povondraite, here for rossmanite, here for schorl, here for tsilaisite and here for uvite, and here for vanadio-oxy-chromium-dravite and here for vanadio-oxy-dravite. Click here for Best Minerals T and here for Best Minerals A to Z and here for Fast Navigation of completed Best Minerals articles.

Can you help make this a better article? What good localities have we missed? Can you supply pictures of better specimens than those we show here? Can you give us more and better information about the specimens from these localities? Can you supply better geological or historical information on these localities?



Tourmaline Group
Tourmaline is perhaps the main repository for boron in the earth's crust. Its stability field ranges from as low as 150°C and perhaps lower and pressures as low as 150 MPa (~150 atmospheres)1 and as high as 725 to 950°C depending on the pressure and composition.2 60 (kbar) kilobars pressure. Tourmaline has a complex structure where many elements can enter into its composition and, because of this, the study of these elements and their location in the structure, tourmalines can open a window on the conditions under which they were formed and the rocks rocks that contain them. An issue in the Canadian Mineralogist in 2011 says that the study of tourmaline shows "that we are standing on the brink of a major breakthrough in the use of tourmaline as a quantitative indicator of the chemical and physical properties of its host environment." These properties may well make tourmaline the prime mineral for this purpose though some scientists knowledgeable in the field think the idea has been oversold. Tourmalines are found in many geological settings. Pegmatites produce many of the specimens cherished by collectors, some of which are pictured here, but tourmalines are also commonly found in granites and in metamorphic rocks like schist, shale, marble, conglomerate, lodestone and limestone. Because of their stability they are also found in sedimentary and meta sedimentary rocks. Under diagenetic conditions, tourmaline can develop as overgrowths on detrital tourmaline cores or as new, authigenic crystals.
1. Henry et al. 1999, More et al. 2004 2. Robbins & Yoder 1969, Holtz & Joannes 1991, Krosse 1995, Morgan & London 1989, Wolf & London 1997, von Goerne et al. 1999, Spicer et al. 2004, Ota et al. 2008a, London 2011.

Of all the different tourmaline species, black tourmaline, probably mostly schorl, is by far the most abundant and may account for 90% or more of the earth's tourmaline. Schorl has the longest history and can trace its description back to German localities in the 1400's and to various tin mines in the Erzgebirge. Some black tourmalines are found abundantly in mica schist and some localities produce thousands of well formed crystals, sometimes of considerable size (fist size and larger). They are also found in the cap rock of salt domes as are the povondraite specimens from Bolivia pictured below. At the Kami tin mine in Bolivia there are thousands, perhaps millions of tons of tourmaline rich rocks associated with the tin veins there. It was so abundant that during the second world war the Japanese, who had great difficulty getting borates, set up a refinery to recover boron from the rocks there. Tourmalines are even found in environments like magnesite deposits, like the one at Brumado in Minas Gerais, Brazil where they are commonly found as uvite.

Below are listed the current members of the tourmaline group of minerals. There are two philosophies about naming minerals. One we will call the splitters and the other the lumpers. The splitters want to give a new mineral name to every slight variation of composition and structure. Opposing them are the lumpers who would do away with many of the current mineral names. The lumpers might be personified by the late Dr. Fred Pough, one time curator of the mineral collection at the American Museum of Natural History. On more than one occasion I heard him say approximately this: "What's the matter with tourmaline? Tourmaline is a perfectly good name; you don't need all of these varieties to have their own names." Other knowledgeable current researches in the field also feel this way. Every mineral person worth their salt has their own opinion about what should be done about this mess and, at times, even the IMA vacillates on the subject. One can't but feel sympathy with the lumpers when confronted with tourmaline crystals like the two immediately below. Each has three different tourmaline end member components and possibly more in its structure. Many collectors would like to use one name to name them but also feel uncomfortable calling them tourmaline because of the research in recent years has clearly shown that there are many different kinds of tourmaline. If you don't know for sure the chemical composition of your tourmaline specimens, there is no way you can give it the name of a tourmaline species with assurance, so you are better off just calling it tourmaline. However, the considerable implications of the composition of various kinds of tourmalines in relationship to what they can tell us about the conditions that formed them and the rocks that host them requires that we be as careful as we can about tourmaline species names. I fear that it will take a long time for this reality to soak into the minds of mineral collectors and specimen dealers. Both usually want a definite name to call a particular tourmaline crystal and don't want to confuse the issue with complicated mineral names like Foitite 12%/rossmanite 23%/elbaite 65%.

Olenite/elbaite & schorl 4.3cm, Burma© Lavinsky
Foitite/rossmanite/elbaite 2.2cm Elba, Italy© Kohorst

Of all of the many specimens of tourmaline shown below and the links to many others, only a very few crystals of tourmaline have been adequately characterized to determine which end member components they contain. In the case of the pink mushroom type from Burma above, perhaps only two have been characterized. It was found that the predominate tourmaline species near its tip was olenite which graded into elbaite and then into black schorl at its base. It may be that all similar crystals have this same arrangement of tourmaline species in them, but drawing a firm conclusion about them based on such a small number of analyses is a risky business. Many of the tourmalines shown in this article will never be analyzed because to do so would require that they be cut up to gain access to their interiors. The same is true of the crystals from Elba which may contain rossmanite.
Andreas Ertl, John M. Hughes, Stefan Prowatke, Thomas Ludwig, Franz Brandstätter, Wilfried Körner, and M. Darby Dyar (2007) TETRAHEDRALLY COORDINATED BORON IN Li-BEARING OLENITE FROM “MUSHROOM” TOURMALINE FROM MOMEIK, MYANMAR.

There are certainly tourmalines from other localities that have multiple end member components in their structure, but the number of tourmaline crystals that have been accurately characterized is a vanishingly small percentage of all tourmalines. Also, it is not a simple thing to correctly analyze a tourmaline; you can't just look at the color and know what it is. So when you are looking at tourmalines that have been given specific tourmaline group names, it has been done so on the basis of very few analyses of crystals from any particular locality and in most cases is just a best guess on the part of the collector, curator or mineral dealer. Many pegmatites are rich in fluorine for instance, and in those pegmatites one could expect that some if not all of the tourmalines found at that locality may be of the fluor end member composition. Zoning in tourmalines is common, not only from top to bottom, but also from the core outward. Some of this zoning is obvious in transparent and translucent crystals and is one of the reasons why collectors are so attracted to them. The more vivid the color change and the more colors a tourmaline crystal has, the more desirable it is to collectors. Studies have shown, that opaque tourmalines, commonly the black and brown ones, also can have significant compositional zoning.

Each of the tourmaline group names listed below is linked first to its species page on Mindat and then to an individual Best Minerals article that tells more about each species and in some cases shows many more pictures of that particular kind of tourmaline. To see that article just click on the part of the line that says: "Click here for the Best Minerals XXXXX..."
[Rock Currier 2012]



Buergerite is currently currently not a recognized species. It was recognized as a species in 1966 when specimens were abundant compared to today but, in 2011 was renamed fluor-buergerite because of its fluorine content in 2011. The reason this name is maintained here in the tourmaline group is because of the very many specimens in collections around the world. It will take generations for most of the labels to be corrected.
Henry, D., Novák, M., Hawthorne, F.C., Ertl, A., Dutrow, B.L., Uher, P. & Pezzotta, F. (2011): Nomenclature of the tourmaline supergroup minerals. Am. Mineral., 96, 895-913.


Chromium-dravite: Trigonal: Click here for Best Minerals Chromium-dravite.
Na(Mg3)Cr3+6(Si6O18)(BO3)3(OH)3(OH) This is the only picture of Chromium-dravite we have in our database at this time (20 April 2013). The chromium-dravite are the green grains in the rock.

Chromium-dravite, Zaonezhie peninsula
Karelia Republic, Russia 2cm tall
© 2007, JGW



Chromo-alumino-povondraite?: Trigonal: Click here for Best Minerals Chromo-alumino-povondraite.
Na(Cr3)Mg2Al4(Si6O18)(BO3)3(OH)3O
The chromo-alumino-povondraites are the rounded equant emerald-green grains (which were initially mistaken for uvarovite!), embedded in massive aggregate of elongated pale green to whitish tremolite crystals.

Chromo-alumino-povondraite & tremolite
Balmat, New York, USA FOV 1.5mm
© Vincent Bourgoin 2012



Darrellhenryite: Trigonal, click here for Best Minerals darrellhenryite.
[[b]Na(LiAl2)Al6(BO3)3Si6O18(OH)3O[/b]

Darrellhenryite, Czech Republic, Bohemia 3.5cm wide©


Mindat lists only one locality for this new tourmaline group member which is the type locality: Nová Ves, Český Krumlov, South Bohemia Region, Bohemia (Böhmen; Boehmen), Czech Republic. Mindat has no pictures of this mineral (May 2013)



Dravite: Trigonal: Dravite-Elbaite Series, Dravite-Schorl Series. Click here for Best Minerals Dravite.
Na(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH) Quite a few nice specimens are pictured in the dravite article.

Dravite & Magnecite, Brumado, Bahia, Brazil 7.5cm wide© Verrier.Frédéric



Elbaite: Trigonal: Elbaite-Liddicoatite Series, Dravite-Elbaite Series, and the Elbaite-Schorl Series. Click here for Best Minerals Elbaite, Afghanistan to Nigeria and here for Best Minerals Elbaite, Pakistan to Zambia. Many valuable specimens shown here.
Na(Li 1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)

Elbaite & Quartz, Queen Mine, Pala, San Diego Co. California, USA ~17cm wide© J.Ralph



Feruvite Trigonal: The Fe2+-analogue of uvite. Click here for Best Minerals feruvite.
Ca(Fe2+)3MgAl5(Si6O18)(BO3)3(OH)3(OH)
There are only 14 localities for this tourmaline species but we have pictures of only two specimens from a Japanese locality.

Feruvitre & diaspore, Kiura mine, Saeki city, Oita prefecture, Japan 3.6cm© R. Tanaka



Fluor-buergerite Click here for Best Minerals fluor-buergerite. Mindat currently lists only four localities for this mineral (2013)
Na(Fe3+3)Al6(Si6O18)(BO3)3O3F

Fluor-buergerite 15cm, Mexquitic, San Luis Potosí, Mexico© Rob Lavinsky



Fluor-dravite: Trigonal: The F analogue of dravite. Click here for Best Minerals Fluor-dravite.
Na(Mg3)Al6(Si6O18)(BO3)3(OH)3F

Fluor-dravite© Chamberlain


A 3.5cm specimens of fluor-dravite from Cream of the Valley Road, Gouverneur, St. Lawrence Co., New York, USA


Fluor-elbaite: Trigonal: The F-analogue of elbaite. Click here for Best Minerals Fluor-elbaite.
Na(Li 1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3F

Fluor-elbaite, 1.7cm, Cruzeiro mine, M.G, Brazil©



Fluor-feruvite: The hypothetical F-analogue of feruvite. Click here for Best Minerals Fluor-feruvite.
Ca(Fe2+)3MgAl5(Si6O18)(BO3)3(OH)3F
Fluor-feruvite is listed in Mindat's locality database from only one locality: Fort Hope pegmatite field, Fort Hope, Kenora District, Ontario, Canada. We have no images of this mineral and list it as the hypothetical fluorine analogue of feruvite.


Fluor-liddicoatite, Trigonal, the F-analogue of liddicoatite. Click here for Best Minerals Fluor-liddicoatite.
Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3F

Fluor-liddicoatite to 7cm. Anjanabonoina pegs, Betafo Dist. Antananarivo Province, Madagascar © E. Marini



Fluor-schorl: Trigonal: The F-analogue of schorl. Click here for Best Minerals Fluor-schorl.
Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3F

Fluor-schorl, Lake Boga, Victoria, Australia© Mills



Fluor-tsilaisite: Trigonal: The F analogue of tsilaisite. Click here for Best Minerals fluor-talasite.
Na(Mn2+)3Al6(Si6O18)(BO3)3(OH)3F trigonal

Mindat currently has no images of fluor-talasite (May 2013).



Fluor-uvite Click here for Best Minerals fluor-uvite
Ca(Mg3)MgAl5(Si6O18)(BO3)3(OH)3F trigonal

Fluor-uvite ~1.5cm, Reese Farm, Gouverneur, New York, USA© Betts



Foitite: Trigonal: A vacancy-dominant member of the Tourmaline Group.
Correct identification is only possible by suitable analytical methods. Click here for Best Minerals Foitite.
(□,Na)(Fe2+2Al)Al6(Si6O18)(BO3)3(OH)3OH

Foitite cap on liddicoatite© Matteo


A liddicoatite crystal with a foitite cap and a schorl base 8.1mm, Rosina vein, San Piero in Campo, Campo nell'Elba, Elba Island, Livorno Province, Tuscany, Italy



Liddicoatite: Trigonal: Elbaite-Liddicoatite Series. Click here for Best Minerals Liddicoatite.
Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3(OH)
Note on the nomenclature: the "liddicoatite" holotype (Dunn et al., 1977) is F-dominant on the W-site, although the originally suggested formula was OH-dominant. Therefore the type material has been redefined as fluor-liddicoatite (Henry et al., 2011); "liddicoatite" is currently a non-approved species. Most "liddicoatites" appear to be F-dominant, and therefore fluor-liddicoatite. Note on the nomenclature: the "liddicoatite" holotype (Dunn et al., 1977) is F-dominant on the W-site, although the originally suggested formula was OH-dominant. Therefore the type material has been redefined as fluor-liddicoatite (Henry et al., 2011); "liddicoatite" is currently a non-approved species.




Luinaite-(OH): Monoclinic
Na(Fe2+)3Al6(Si6O18)(BO3)3(OH)3(OH)

Lunaite-(OH) 11cm wide, Mt Bischoff mine, Waratah, Tasmania, Australia© A. Tuma


Mindat currently lists 9 localities luinaite-OH. The type locality for luinaite-OH is Mt Cleveland Mine, Luina, Heazlewood district, Tasmania, Australia.



Magnesiofoitite: Trigonal: Click here for Best Minerals magnesiofoitite.
(□,Na)(Mg2Al)Al6(Si6O18)(BO3)3(OH)3(OH)

Magnesiofoitite & quartz, 6.2cm© Jiangbin


Huya W-Sn-Be deposit (Pingwu beryl mine), Huya township, Mt Xuebaoding, Pingwu Co., Mianyang Prefecture, Sichuan Province, China



Olenite: Trigonal: Click here for Best Minerals Olenite.
Na(Al3)Al6(Si6O18)(BO3)3O3(OH)

Olenite 7cm wide, Curiglia, Varese Province, Lombardy, Italy© Sarah Sudcowsky


Oxy-chromium-dravite. Click here for Best Minerals oxy-chromium-dravite.
Na(Cr)3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O

Mindat lists one locality for oxy-chromium-dravite which is the type locality of Pereval Marble Quarry, Slyudyanka (Sludyanka), Lake Baikal area, Irkutskaya Oblast', Prebaikalia (Pribaikal'e), Eastern-Siberian Region, Russia. Mindat currently has no images of this mineral (May 2013)



Oxy-dravite: Trigonal: Click here for Best Minerals Oxy-dravite.
Na(MgAl2)MgAl5(Si6O18)(BO3)3(OH)3O

Oxy-dravite, Alto Chapare District, Cochabamba Department, Bolivia© 2008, JGW



Oxy-rossmanite: Not yet approved by the IMA. A preliminary working name for a hypothetical new member of the tourmaline group. Click here for Best Minerals Oxy-rossmanite.
☐(LiAl2)Al6(Si6O18)(BO3)3(OH)3O
A preliminary working name for a hypothetical new member of the tourmaline group. Not an IMA approved mineral.



Oxy-schorl: Trigonal: Click here for Oxy-schorl.
Na(Fe2+Al)3Al6(Si6O18)(BO3)3(OH)3O
"Schorl" with O>OH,F on the W site; not uncommon, but can be reliably identified only from detailed and quantitative chemical analyses.
Originally used as a working name and published without approval, then finally approved in 2011. IMA status: Approved 2011



Oxy-vanadium-dravite: Not to be confused with vanadio-oxy-dravite. Click here for [www.mindat.org]
Best Minerals Vanadium-dravite.
Na(Mg,Fe2+)3(V3+,Cr3+,Al)6(Si6O18)(BO3)3(OH)3(OH) trigonal

Vanadium-dravite, FOV 2.5mm, Lake Onega, Karelia Republic, Russia



Povondraite: Trigonal: Click here for Best Minerals Povondraite.
Na(Fe3+3)Mg2Fe3+4(Si6O18)(BO3)3(OH)3O

Povondraite 7cm wide© Alfredo Petrov



Rossmanite: Trigonal, Vacancy-dominant member: Identification only possible with quantitative chemical analysis and/or crystal-structure refinement. Click here for Best Minerals Rossmanite.
☐(LiAl2)Al6(Si6O18)(BO3)3(OH)3(OH)

Rossmanite xl 2.2cm© Kohorst

Grotta d'Oggi Quarry, San Piero in Campo, Campo nell'Elba, Elba Island, Livorno Province, Tuscany, Italy. At least its mostly rossmanite. It has a yellow elbaite base with a central portion of white rossmanite with a black foitite cap.



Schorl: Trigonal: Elbaite-Schorl Series, Dravite-Schorl Series. Click here for Best Minerals Schorl.
Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)

Schorl & Quartz 10.5cm, Erongo Mountain, Erongo Region, Namibia© Schnaitmann



Tsilaisite : Trigonal: The OH analogue of fluor-tsilaisite. Click here for Best Minerals Tsilaisite.
Na(Mn2+)3Al6(Si6O18)(BO3)3(OH)3(OH)

Tailaisite, FOV 1.3mm, San Piero in Campo, Elba, Italy© Yaiba Sakaguchi



Uvite Click here for Best Minerals Uvite
Ca(Mg3)MgAl5(Si6O18)(BO3)3(OH)3(F/OH) trigonal

Uvite on quartz 3.5cm tall© Weinrich


Uvite is a continuous series between its OH (hydroxy) and F (fluor) end members. Since we have many images of uvite and don't know if they are F or OH we are calling them uvite. The F (fluorine) rich variety is the most common kind of uvite.


Vanadio-oxy-chromium-dravite The V analogue of oxy-chromium-dravite. Click here for Best Minerals vanadio-oxy-chromium-dravite
Na(V)3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O

Mindat has no pictures of this mineral (May 2013]. This mineral thus far is a one locality mineral. The type locality for the mineral is Pereval Marble Quarry, Slyudyanka (Sludyanka), Lake Baikal area, Irkutskaya Oblast', Prebaikalia (Pribaikal'e), Eastern-Siberian Region, Russia.



Vanadio-oxy-dravite Click here for Best Minerals vanadio-oxy-dravite.
NaV3(Al4Mg2)(Si6O18)(BO3)3(OH)3O

Mindat has no pictures off this mineral (May 2013). It is a one locality mineral and the type locality is Pereval Marble Quarry, Slyudyanka (Sludyanka), Lake Baikal area, Irkutskaya Oblast', Prebaikalia (Pribaikal'e), Eastern-Siberian Region, Russia. It was named for its vanadium content and relationship to dravite.




Click here to view Best Minerals and here for Best Minerals tourmaline group minerals, here for Best Minerals chromium-dravite, here for chromo-alumino-povondraite, here for darellhenryite, here for dravite, here for elbaite, Afghanistan to Nigeria, here for elbaite, Pakistan to Zambia here for feruvite, here for fluor-buergerite here for fluor-dravite, here for fluor-elbaite, here for fluor-feruvite, here for fluor-liddicoatite, here for fluor-schorl, here for fluor-tsilaisite, here for fluor-uvite, here for foitite, here for liddicoatite, here for luinaite-(OH), here for magnesiofoitite, here for olenite, here for oxy-chromium-dravite, here for oxy-dravite, here for oxy-rossmanite, here for oxy-schorl, here for oxy-vanadium-dravite, here for povondraite, here for rossmanite, here for schorl, here for tsilaisite and here for uvite, and here for vanadio-oxy-chromium-dravite and here for vanadio-oxy-dravite. Click here for Best Minerals T and here for Best Minerals A to Z and here for Fast Navigation of completed Best Minerals articles.


[First draft finished in June 2013]

Rock Currier
Crystals not pistols.



Edited 138 time(s). Last edit at 09/10/2014 05:48AM by Alfredo Petrov.
Re: Tourmaline group
May 03, 2012 03:11PM
Rock,
Thanks for posting this. it is academically interesting, but I even more appreciate the quote from Mr. Pough. Where does the quote end? Is it the whole rest of the paragraph? Sounds like it. I sympathize w/ the lumpers now, but as technology gets better, I'll pity the splitters, because they'll "tilt" from the overload, I suspect! But if it makes 'em happy, fine, more power to 'em. This hobby does get as deep as you want to go...
Re: Tourmaline group
May 03, 2012 03:35PM
Hi to everybody!
Ok these are the current members of tourmaline group which are officially recognized as mineralogical species. Nevertheless there is an important problem: how can we distinguish a fluor-dravite from an oxy-dravite and these two species from a dravite? It is necessary to have a chemical analysis and therefore destroy the specimen, at least in the biggest majority of cases! It seems a sort of blaspheme for a gemologist!
Greetings from Italysmileys with beer by Riccardo
avatar Re: Tourmaline group
May 03, 2012 09:33PM
D Mike Reinke,
I have put in the missing quote mark. I am not really sure what the final shape of this article will be. Currently I want to get a picture of a tourmaline that George Rossman showed me that had three tourmaline species in it and us that for the lead into the article. Then I think I will put what ever I judge to be the best example of the various tourmalines we have with each of the tourmaline group species listed along with comments about them. I think I will then create an article on each tourmaline group species with a complete an array of the best images we have along with further comments, hopefully helped out by people like you.

Rock Currier
Crystals not pistols.
avatar Re: Tourmaline group
May 03, 2012 09:37PM
Ricardo,
I don't know the answer to your question. But your comment is interesting. Perhaps you would care to write it up in a bit more detail with reference to the various tourmaline species? That could very well fit into the article. I am, by the way, willing to post different points of view regarding this. When this is done, I think people reading it will find it more instructive than reading just one point of view. More than likely they will be similar to discussions among the nomenclature group in the IMA.

Rock Currier
Crystals not pistols.
Re: Tourmaline group
June 14, 2013 02:59PM
Is Indicolite not a actual type of Tourmaline, or is that one recognized officially as a variety of Elbaite (as the only blue I saw above was Fluor-Elbaite)? I just obtained a lot of blue Tourmaline (all blue, no schorl) from Afghanistan, they were sold as Indicolite and I have always been referring the blue Tourmalines as such. Is this not the case?
avatar Re: Tourmaline group
June 15, 2013 10:53AM
Scott,
Indicolite is a general unofficial name for blue tourmaline. The IMA (International Mineral Association) is a group of mineralogists made up of mineralogists from all over the world. Each country that has a professional mineralogical association like the American Society of America nominates a mineralogist to be that countries representative to the IMA. The IMA has a committee that oversees the naming of minerals, and it that list of official minerals that this website uses as real official mineral names. However they don't try and regulate mineral names that are used historically or by various trade groups or other groups of people like metaphysical practitioners. Indicolite is one of those many unregulated names that are popular with non mineralogists and have more or less gained acceptance as meaning blue tourmaline. But like ruby, it is a general term and everyone argues about about how much green a blue tourmaline has to have before it is not longer indicolite or how pink a ruby must be before it is no longer a ruby. The IMA won't allow themselves to get sucked into this kind of argument. There is no practical way to settle it. It is only in the eye of the beholder. People selling pink sapphires like to call them rubies because it is a higher value name and of course people buying them want to call them sapphires to negotiate on the basis of a lower value name. A number of tourmaline species can be blue or have a bluish color. I hope the above comments may be helpful to you.

Rock Currier
Crystals not pistols.
Re: Tourmaline group
October 04, 2014 04:18PM
I'm kind of with Bill Larson on the topic of what to call your tourmaline, at least in a general descriptive sense. It's all tourmaline. The mineralogical references typically identify "End Members" of essentially fixed chemical composition, and as we all know there are few specimens of tourmaline that adhere to that formulation. The architecture of the tourmaline structure allows for anion substitution in most of its sites, thus creating a solid solution nightmare. There are likely no "pure" liddicoatites or elbaites. And from my perspective, unless a mineral specimen comes with an analysis, I won't trust any mineralogical identifications. It's not enough to have a gem tourmaline come from Madagascar to call it liddicoatite! To some degree the "color" names are better, because they avoid the mineralogical confusion. I can see that a specimen is rubellite or verdelite. There the problem arises with those intermediates that are neither pure blue or green, or in the case of some localities, both, and more! To make matters worse, you now have locality references that have made their way into the gemological culture, such as "Paraiba". Bill prefers to call them all "tourmaline", supplying the appropriate modifiers as necessary. Modifiers such as "Ca-rich", "deep red", "gemmy" or "multicolor" are perfectly appropriate, as long as you know that aspect of the stone.

I'd like to shamelessly plug yet another tourmaline term. There are many specimens that have been classified as schorl, simply because they appear dark, but many of these so-called "schorl" will pass visible light. I prefer to identify these as "lucidemite", to distinguish them from the opaque varieties.
avatar Re: Tourmaline group
October 04, 2014 09:34PM
Curtis,
I think you are just voting in favor of one view of tourmaline. These two competing views were discussed above in the introduction to the tourmaline group as a conflict between the splitters and the lumpers. "The lumpers might be personified by the late Dr. Fred Pough, one time curator of the mineral collection at the American Museum of Natural History. On more than one occasion I heard him say approximately this: "What's the matter with tourmaline? Tourmaline is a perfectly good name; you don't need all of these varieties to have their own names."

Obviously you and Bill are lumpers and believe, me having had to endure writing the article knowing full well that I am not an expert on tourmaline makes me appreciative of your view point. However the purpose of the article is to try and present a bit of the current modern day thinking and knowledge about tourmaline along with a bit of historical perspective as well. The article was purposely written not to take sides in the argument but to give both a fair hearing and let the reader decide how he wants to label the tourmalines in his collection. I managed to hornswaggle Dr. David London into reviewing the text and thanks to his efforts I have thus far been kept out of trouble at least to the extent that I have apparently thus far not been branded a complete dummy.

I suspect that future nomenclature changes in the future will require further revisions of this article.

Rock Currier
Crystals not pistols.
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