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 Post subject: Gemstone names and classification
PostPosted: Mon Jun 18, 2007 12:33 pm 
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I think that my name problem and keeping them straight is that I need a way to classify Gems. I have been through many gem and mineral sites looking for some sort of standard way to outline them but could not find one.

By combining information from various sites I tried to construct one. It is they only way I keep the various names straight.

I have used beryl as an example:

Series:

Variety:

Trade Names:
Brand Names:
Misnomers:

Series
A series is a mineral group consisting of minerals that have a nearly identical crystal structure. The only difference between the minerals in a series is the type of elements contained in the crystal structure of the mineral.

Variety
Titled variable of a mineral, characterized by a special property not present in other members of that same mineral (such as color, location,)



Beryl
1. Aquamarine
Maxixe
True Blue
Santa Maria
2. Red Beryl
Bixbite
Red Emerald
3. Emerald
Trapiche
4. Green Beryl
Vandium Beryl
Riesling
5. Goshenite
6. Heliodor
7. Morganite
8. Pezzottaite

Even this is confusing me. Should Heliodor be under Yellow Beryl, as not all shades of yellow are called Heiodor? Am I even warm? Would appreciate any input.

Roberta


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PostPosted: Mon Jun 18, 2007 4:31 pm 
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RAW-

I trust that you have also looked at The Gemology Project (see the link to the left.) It is a work in progress, but already may be of some help. There are some really good sites on general mineralogy that I hope you have visited (www.webmineral.com is an example).

Anyway, with respect to mineral gemstones (gems other than pearls, coral, amber, and the like), they are all classified under the rules of mineralogy. You will see Dana classifications, also Strunze classifications, both of which use a numerical systems somewhat like a card catalog system used in a library. For example, these consider chemical composition and crystal systems, optical characters, and other criteria, as a way to uniquely classify minerals. Unfortunately naming has a long history, and in more than one culture, so duplicate names often arose for the identical mineral.
An effort has been made (via an international authority) to straighten out the mess by using rules of precedence, similar to those used in biological taxonomy. That has helped get rid of discredited and duplicate names. That process is what led to restoring the older names "almandine" and "spessartine" to replace "almandite" and "spessartite" that had come into usage after an earlier spasm of re-naming aimed at inifying mineral names to use the "-ite" suffix. (These are just examples.)
Unfortunately the world of gems pays little attention to the efforts of the scientific community. Also local vernacular and marketing efforts cause retention of such old names as "topaz" for yellow quartz and sometimes even yellow sapphire. And we get nonsensical names like "green amethyst" or "red emerald" or even "pink emerald" when accurate names already exist. Even very reputable and supposedly knowledgeable gem dealers perpetuate some real howlers, like labeling yellow or yellowish green spodumene "hiddenite" or "yellow kunzite."
Your efforts have already begun to sort out some of the mess where gem terminology is concerned. After the formal classifications under the rules of mineralogy, you all too frequently encounter trade names, like Tanzanite and Tsavorite. You will also find a lot of importance placed on geographical origin, sometimes for good reason. But here again the marketers subvert the name by calling certain sapphires "Kashmir" and certain tourmalines "Paraiba" irrespective of actual provenance.
I should mention the additional confusion caused by heating, diffusion, irradiation, and similar treatments that change the material to something perhaps not found in nature (or extremely rare).
We cutters often really split hairs, so that in discussions of garnet, for example, there is Umba garnet, and there is Malaya garnet, and there is Mandarin garnet, and there is Rhodolite garnet. Not to mention Mali garnet and Merelani Mint! Poor old almandine and pyrope are left in the dust!

Quite a bit of background info is to be found on this site, sometimes in surprising threads, perhaps not really on the subject of naming, but with some of the local experts offering their knowledge. All I can suggest is to keep on reading everything you can find, and keep an open mind with plenty of healthy skepticism.

Just my few thoughts. A bet a lot of the old hands here will weigh in with many more.

-Dick Davies


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PostPosted: Mon Jun 18, 2007 10:09 pm 
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Dick,
Thank you so much for your reply. I have looked at the various sections on this site including the free gemology courses. I quess I got lost in the semantics, and it seemed that every other site including the minerology sites seemed to classify gemstones differently so I thought that minerologists used a different system from gemologists.

For instance one site said that olivine was under fosterite and another said the reverse, but peridot was under both. Some also included chrysolite, which may be yellow gold or yellow brown or yellow depending on where you look. Is chrysolite a gemstone? Another site still said that it was (golden yellow peridot).

One gem site did start with Dana Classification, but the rest seemed to start with crystal systems. Is there an industry standard for gemstones, because it seems that everyone is making it up as they go or all saying the same thing in every way possible.

I am just desperatly looking for a starting point outlining gemstones so I can file their names correctly and understand what is what.

I just can't even go into garnets at this point, or treatments.

Again, thank you for your help.
Roberta


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PostPosted: Tue Jun 19, 2007 12:14 am 
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There you go!. Peridot is a gem name for what is often called "olivine," which is actually a series with forsterite(magnesium silicate) on one end and fayalite (iron++ silicate) on the other. Peridot is almost always somewhere in the middle, with the lighter greener and more attractive specimens closer to the forsterite end, while the browner ones close to the fayalite end with more iron are not attractive as gems. Gem peridot gets its color from the ferrous iron in its makeup. Occasionally some of the peridot from Pakistan is almost colorless. These crystals and nodules are often imbedded in soft white alteration products rich in magnesium, such as magnesite and talc, or possibly serpentine. Some of the more attractive greens may (according to some experts) also contain a trace of chromium. "Chrysolite" is one of those old names not much used any more, but has been used as a synonym for peridot. But it sometimes was a synonym for something else, such as prehnite!

This site attempts to help make sense of it all by discussing (and cussing) some of the baffling irregularities and inconsistencies that so often get in the way of intelligent discourse. Also, you can't believe every bit of "information" you find just because it is on the web. There is a lot of erroneous and incomplete information out there. I saw some the other day that tried to be authoritative, but was out of date by about 100 years or so!

I think you are always safe to begin by using the true mineral name, then cross-reference to the gem forms of the mineral. Quartz, then would have many crystalline and cryptocrystalline forms listed that would include amethyst, citrine, agate, chalcedony, etc. Under beryl you would have the usual suspects as you noted at the beginning of this thread.

Your understanding will be greatly enhanced if you have a few inorganic chemistry courses under your belt, including qualitative analysis. Also an understanding of how rocks are formed and how different rock compositions arise and lead to the special conditions that are a pre-requisite for gem minerals. For example, if you see free quartz in a rock sample, you won't find corundum there. That's because the two minerals would have combined into sillimanite or kyanite or another aluminum silicate, instead. The free quartz acts as an acid. So rubies and sapphires are found in basic metamorphic rocks such as crystalline marbles and dolomites, or sometimes in basic extrusive rocks like some basalts.

Another really great example accounts for the rarity of fine emerald as compared to the relative abundance of common beryl or even aquamarine. It is because magma tends to undergo gravitational and chemical separation of chromium long before it gets close enough to the surface to begin to crystallize into granite-like rock. The light elements that go into beryl, topaz, tourmaline, and the like tend to be the very last things to crystallize. So it takes a rare accident to bring some of that late broth of light elements into contact with a host rock that happens to contain enough chromium to create the color in emerald.

Probably you will just have to learn as much as you can about each gem mineral using all available sources so you can discard the erroneous stuff while retaining the accurate material. Feel free to ask questions on this site as well, because that is it s purpose. Then tackle those pesky garnets!

-Dick


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PostPosted: Tue Jun 19, 2007 1:05 am 
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RichardD
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We cutters often really split hairs, so that in discussions of garnet, for example, there is Umba garnet, and there is Malaya garnet, and there is Mandarin garnet, and there is Rhodolite garnet. Not to mention Mali garnet and Merelani Mint! Poor old almandine and pyrope are left in the dust!

I don't believe "you cutters" are splitting hairs—only using names which convey useful information. Your terms Mandarin, Mali, and Merlelani Mint are acceptable "trade names" which, if mineralogists had any real interest in garnets, have the possibility of becoming recognized color varieties.

On the other hand, "poor old" almandine and pyrope are recognized species, the names of which do not describe any particular color and are of little use in describing the appearance of a stone.

Finally, there are the terms Rhodolite (a mineralogically recognized color variety), and Malaya (a trade name) which are basically mixtures of Pyrope and Almandine or Spessartine and have "characteristic " colors. Unfortunately the GIA does not like the idea of the "proper" terms like "pyrope-almandine or pyrope-spessartine." Apparently they have little sales appeal. Consequently, they instruct their students treat these materials as new species—thus converting color varieties into species.

With reasoning like that, gemological nomenclature is in serious trouble.


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PostPosted: Tue Jun 19, 2007 3:02 am 
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Quote:
Your understanding will be greatly enhanced if you have a few inorganic chemistry courses under your belt, including qualitative analysis. Also an understanding of how rocks are formed and how different rock compositions arise and lead to the special conditions that are a pre-requisite for gem minerals. For example, if you see free quartz in a rock sample, you won't find corundum there. That's because the two minerals would have combined into sillimanite or kyanite or another aluminum silicate, instead. The free quartz acts as an acid. So rubies and sapphires are found in basic metamorphic rocks such as crystalline marbles and dolomites, or sometimes in basic extrusive rocks like some basalts.



I don't think that at this point of my life I will be getting any chemistry or qualitative analysis courses, but I have been reading on how rocks are formed from my various Rock and Mineral books and a geology book I purchased. However your descriptions are much easier to understand than any I have read so far.

Roberta


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PostPosted: Tue Jun 19, 2007 12:00 pm 
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Hi,

I hope you guys realize that there are people out there (here) that crave for you sharing that knowledge.
While we do Saturday chats on basic gemmology, we have now introduced more advanced chats on Sunday. Brian is doing excellent work in the latter.

If any of you who have real good information to share on a specific topic at an advanced level (and can do it on a weekend chat), please let me know. Some of us are really interested in it.


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PostPosted: Tue Jun 19, 2007 12:11 pm 
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RawRocks wrote:
I'm looking for some sort of standard way to outline them but could not find one.


I'm thinking, perhaps your desire to outline may be premature. I would try to get a more encompassing picture before pigeon-holing.

Read through the Free Gemology courses on the left.
Invest in the books recommended by Dr. Barbara Smigel.

When you feel more comfortable with the bigger picture, you will be better able to organize your material in a way that makes sense to YOU.

Doos was kind enough to share the organization Gem-A uses for their recommended "Flash Cards":
Quote:
* Group
**Species
***Variety
Tradenames: ..:
....etc

As in:
* Tourmaline
** Elbaite
*** Red tourmaline
Trade names: rubelite
....


But there are so many exceptions, where this classification scheme is much more than necessary or completely inadequate. In order to know which end of the stick you might be on, I would recommend a basic gemological foundation FIRST.


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PostPosted: Tue Jun 19, 2007 12:20 pm 
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Hi,

I'm not sure if Gem-A would agree with that in full .. it was my example on how to organize if one really wants to.


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PostPosted: Tue Jun 19, 2007 12:57 pm 
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Quote:
Doos was kind enough to share the organization Gem-A uses for their recommended "Flash Cards":
Quote:
* Group
**Species
***Variety
Tradenames: ..:
....etc

As in:
* Tourmaline
** Elbaite
*** Red tourmaline
Trade names: rubelite
....


Thank you Barbara and Doos, this is something I can make sense of and use.

I have been reading through all the information on this site and have been through the free gem classes several times, and I will continue to go back through them many more times. My poor brain can only absorb so much at once, so repatition is my friend.

As for books, (I for the most part only read reference books) so for I have read or gone through:

National Audubon Society Field Guide to North American Rocks and Minerals
Simon I Schuster’s Guide to Rocks and Minerals
Colored Gemstones Buying Guide -- Antoinette Matlins
Diamonds and Precious Stones -- Patrick Voillot
A Guide to Field Identification Rocks and Minerals -- Charles A Sorrell
Rocks and Minerals -- A Golden Photo Guide
Mines Miners and Minerals of Western North Carolin’s Mountain Empire -- Lowell Presnell
Successful Mineral Collecting and Prospecting -- Richard M. Pearl
The Gem Hunter’s Handbook -- Tim Lutz
Secrets of the Gem Trade -- Richard W. Wise
Smithsonian Rock and Gem -- Ronald Louis Bonewitz
The Complete Guide to Rocks and Minerals -- John Farndon
The Field Guide to Geology -- David Lambert and The Diagram Group

I an not counting my various Jewelry Books.

My brain needs to take the information and organize it, something which I am not good at.

I will admit my weakness is the crystal systems, I quess I will have to get some equiptment so that I can actually see what is going on or I will never get it.

Thanks, Roberta


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PostPosted: Tue Jun 19, 2007 1:09 pm 
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You're very welcome Roberta.

Have you checked the flash cards available on the Gemology Project?
Click here for info on kyanite:
http://www.gemologyproject.com/wiki/ind ... le=Kyanite
Image


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PostPosted: Tue Jun 19, 2007 1:56 pm 
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Hi RAW rocks,

Your goal is a little blurry to me (probably my own fault).
Are you trying to memorize properties of gems and need an aid for that, or are you confused on how namecalling is organized?


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PostPosted: Tue Jun 19, 2007 6:08 pm 
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Doos,

More of the latter, there are so many names of the various stones, some accepted and some not, and the almost daily Trademarked Names. I just need a way to sort them out so when I see a name I am not familiar with I can look it up or add it to the outline in the proper place so I can remember what it is. That is why I started looking for a Gemological Standard System for Gemstones and got frustrated when I couldn't find one. Is having a photographic memory a requirement for being a Gemologist?


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