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 Post subject: Re: What is a gemstone?
PostPosted: Sat Aug 14, 2010 6:50 pm 
wolf wrote:
hi Kerensky

.... yes quartz is quartz but if I told you I had a piece of cut quartz you would have no idea what I was holding in my hand. So what you call the stone may have a commercial basis (nobody is in this for the good of their health), but that is the purpose of the Geomolgy is.
It is a field of study that leaves us with useful information about minerals that are pretty, so that we can all talk a common language no matter where we are from.


Yea, verily. But I have unresolved concerns (not that these matter to any except me) about distinctions - and indeed views - that are widely held in the gemmy/jewellery community.

Something is worth, no less and no more, than someone else is prepared to pay for it . That's true but also simplistic. Those such as DeBeers and more recently Al Rosa et al have long since found ways to manipulate the market in diamonds. This is, of course, not unique. In other goods, such manipulation goes back as far as the 17th Cent (e.g. tulip mania). USFTC rules regarding natural, synthetic and "imitation" stones seem to me (for the present) to discriminate in favour of protecting the trade in natural stones. So be it. I have no wish to turn the world upside down but this is of no interest to me (nor, I expect, many others) and I see no inherent and general benefit deriving from it. Is a synthetic stone less inherently attractive than its natural counterpart, cut etc. being equal? I can see treated stones as much more of a minefield. The thought of (say) a ruby, that in its native state is riddled with holes and fissures, being filled with glass and sold pari passu with good quality gems is simply fraud. That said, when we get into the realms or heat treatment, oiling etc, my moral compass becomes far less compelling of me - though I see the commercial compulsion clearly enough.

Finally, there is the question of man-made 'imitations' particularly those of an appearance similar to diamond. The 'industry' lore that these were were developed as imitation diamonds, to take the crust out of the mouths of hard-working diamond dealers, I find suspect. At least in the cases of ZrO2 and Y3Al5O12, I have reason to think that is not so. These were develeoped initially as military/industrial materials, with any jewellery application trailing a long way behind. However, and in the case of CZ in particular, one can see that the remarkable cheapness of CZ AAAAA rough, combined with elements in the trade representing their finished goods less than with complete honesty and the creeping of well cut CZ to over USD 300 per ct (before being put into top-quality settings) causes concern in the jewellery trade. Well that's for them. For me, I find CZ very attractive and a substance that, cut and polish being equal, makes the present price of 'commercial grade' diamonds look very odd. Surely no one (not me at any rate) buys a diamond as an investment but because of its particular beauty. CZ comes closer to that beauty than most can distinguish by sight alone. 'Nuff said. I consider these matters of little importance to me and others also are entirely free to think as they may.

Last edited by Kerensky on Sun Aug 15, 2010 12:08 pm, edited 1 time in total.

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 Post subject: Re: What is a gemstone?
PostPosted: Sat Aug 14, 2010 8:05 pm 
Frank wrote:
As Barbra suggested get a copy of gem tools professional (GTP) This already does what you are planning to do. Bill Wise who wrote the program is a member of the forum and a very nice guy. You can put any amount of values in (hardness, RI, dichroism etc ) and the program will list all gems which fall into those values. It also has a list of gem materials much larger than you are contemplating.

Yes. Thanks to you both. At the price, it's simply a must. That said, I am still left with the issue of info transfer and integration in my wetware. But this tool will more than cover my long-term needs and, for the short term, I can make up a simpler and more limited listing in Excel - starting with quartz.... [-o<

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 Post subject: Re: What is a gemstone?
PostPosted: Sun Aug 15, 2010 3:24 pm 
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Joined: Sun Oct 16, 2005 12:22 pm
Posts: 19711
Location: San Francisco
And just for a little help to get started with quartz,
a couple of my favorite sites:

The Quartz Page
Inclusions in Quartz

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 Post subject: Re: What is a gemstone?
PostPosted: Mon Aug 16, 2010 2:00 pm 
Duplicate post removed - sorry.

Last edited by Kerensky on Mon Aug 16, 2010 2:18 pm, edited 1 time in total.

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 Post subject: Re: What is a gemstone?
PostPosted: Mon Aug 16, 2010 2:14 pm 
Well, GT Pro is installed. What a joy it is and an absolute steal at the price. The gem database is wonderful and is almost exactly (and more) what I had in mind, missing only a link to free-form notes pages for each stone, so that users can, if they wish tie in notes of their own - though such a feature might be of more use to newbies than to any one else. OTOH, the 'test yourself' feature is something both fun and practical for newbies to engage with.

The wealth of information, numeric, textual and pictorial, and the ability at the click of a mouse to sort and re-sort data as required provides a power in apprehension of the material that I think printed material must always lack. Tinkering with this new widget immediately begins to thow up questions in my mind (e.g. 'What the ???? is Sulphur doing here? and 'What are all those zero RI's about?), is only going to add to the pleasure in fully exploring it anad dchasing out the answers. The filling in of some of the (many) gaps in my personal information store is possibly the prime reason I decided to spend the time on things gemmy. The satiation of curiosity is a great pleasure - just so long as that satiation is never quite complete. Many thanks, Frank and Barbra for the recommendation.

The book 'Gems' will come here also in due course. I suspect that, like Jackson's 'English Goldsmsiths and Their Marks', it is a specialist compendium that if if one has an abiding interest in the subject material, one is never completely happy if one cannot lay one's hand on a copy and read it in the comfort of one's own armchair. I think a second-hand copy of a previous edition and in good condition might suit me well enough.

Yes, Quartz *is* interesting isn't it? And The Quartz Page is another great resource. Been reading in there for several days and likely to be so for a quite a while yet. As I'm sure you and Alberto intended, many lessons can be drawn out of learning something about that simple and most ancient of of the mineral oxides. The oldest rock is reportedly Zircon (ZrSiO4) and the removal from it of SiO2 (quartz) then yields the monoclinic ZrO2 to feed skull crucibles around the world where it is transmuted it to the transparent cubic phase.

Not that SiO2 in the form of rock crystal lacks beauty of its own Here's another example, being one of the 'infamous' rock crystal skulls, originally bought by French, British and US museums as wondrous examples of pre-Colombian meso-American art. Sadly, lovely objects though they are, this has now been proved not to be the case. The pics below are of one in the British Museum and it is a proven fake, probably manufactured in the mid-19th Cent, possibly in Germany to the order of a French dealer in pre-Colombian art. I understand that the Smithsonian did even worse; their example (purchased through Tiffanys NY!?) has now been dated to the 20th Cent, possibly from the 1950's...... Caveat Emptor.... Still lovely things though.

File comment: Copyright British Museum
Crystal Skull2.jpg
Crystal Skull2.jpg [ 153.7 KiB | Viewed 902 times ]
File comment: Copyright: British Museum

Sorry about the low quality imagery. The BM does not supply these in digital imagery. I have then in lovely PDF form at almost 2/3 scale but uploading PDF verboten ist.

Crystal Skull1.jpg
Crystal Skull1.jpg [ 121.88 KiB | Viewed 902 times ]
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