Amethyst Necklace

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bernard_ric
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Amethyst Necklace

Postby bernard_ric » Tue Mar 18, 2008 1:19 pm

I bought this necklace [as a present for my partner] at a respected auction house. It was described as being of 9 Ct gold and has tags with 375 on the chain and the larger of the cabochons(?) has 375 stamped on it. It was described as being from the early part of the 20th Century

The question is that there is no maker mark nor indeed a hallmark. Any suggestions please?


http://i70.photobucket.com/albums/i104/ ... cklace.jpg

Thanks you for looking.
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kerangoumar
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Postby kerangoumar » Tue Mar 18, 2008 9:21 pm

hello --

you could give me that necklace any old time! the stones are quite well matched in terms of colour and the facets appear to be well cut; the metal work looks good.

if it does not have hallmarks it isn't british-made. european makers might stamp .375 but won't usually also have the 9ct mark - perhaps your piece is north american.

i know everyone wants the hallmarks and then wants to know to whom they belonged. the sad fact is that even now we don't have names to go with all the marks and vice versa. so the best thing to do is to enjoy this lovely necklace.

ps - if you turn the necklace over and put it onto a very bright white sheet you might be able to see the zoning that is so common in amethysts, and you will see the angles that indicate where and how the crystal grew.
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byron mac donald
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Postby byron mac donald » Wed Mar 19, 2008 3:34 am

Kerangoumar-

HUH? you wrote: "ps - if you turn the necklace over and put it onto a very bright white sheet you might be able to see the zoning that is so common in amethysts, and you will see the angles that indicate where and how the crystal grew." I would be very interested in what you mean by this, would you please explain further?

Best wishes- byron
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kerangoumar
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Postby kerangoumar » Wed Mar 19, 2008 3:55 pm

byron:

all gemstones are composed of crystals. amethyst - rather, the chemical broth that crystallizes into amethyst - grows in layers almost like a tree's rings, and in some cut stones this is very prominent and can be seen when you put the stones face down on a brilliantly reflective surface. the layers are termed lamellae just like the lamellae on the underside of a common field mushroom, except that they are alternating layers of left- and right-handed quartz.

(it is easier for non-gemmologists or neophytes to see the layers this way altho they can be seen looking into the stone with a proper loupe)

there is also a stone called "ametrine" which is purple and yellow-yellowish orange. in that case there is an intergrowth of citrine and amethyst (first cousins) that is visible because the layers are large enough to be seen with the eye only.

and not to forget when one is looking at modern jewellery:

almost all modern amethyst has been cooked. that is to say it is heated un a very hot furnace to the point where the colour is a richer, more intense purple. and depending on the temperature and length of exposure, one can turn an amethyst (a pale, tired-looking, or grossly-banded stone) into a citrine or - the current vogue - a green amethyst.

the necklace in question is an older one and i would be surprised if those stones had been cooked.
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byron mac donald
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Postby byron mac donald » Wed Mar 19, 2008 8:55 pm

Kerangoumar-

Thank you for the very informative information it is very interesting. I can see what you mean about the color on these, they are light.

Byron
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kerangoumar
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Postby kerangoumar » Thu Mar 20, 2008 2:45 pm

byron

they are light only comparatively speaking. if you had a similar necklace set with cooked stones, you might think "wow! these are great stones!" because you have been subtly conditioned to think that darker is richer is better, but in fact these stones, being naturally coloured, are more desirable.

it's a problem with all varieties of coloured stones, because it is very easy to take cheap stones and cook them to the "desirable" colour and thus raise their price. if you are in the market for coloured stones, one of your first questions should be "are these stones enhanced?".
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byron mac donald
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Postby byron mac donald » Fri Mar 21, 2008 2:29 am

Kerangoumar-

No... I do not think I would think that "Cooked stones" would be better, any more than I would believe that man-made diamonds would be. I like things in their natural state and believe they should be considered more valuable as such. I may not know much about natural gems (even though I know a little more with your help) I believe that changing their apperance in order raise value seems un-ethical to me, and should be worth less. And besides, I like the paler color.
At one time I read an article on diamonds; this article explained the difference between old cut, and the modern, I liked the old cut better even though they did not seem to have the same brilliance. I guess I just like the history of things and deem them more valuable.

Regards- Byron
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kerangoumar
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Postby kerangoumar » Fri Mar 21, 2008 2:08 pm

byron -

enhancements are unethical in my book as well but the industry does not have the same qualms.

go into any jewellery store and ask to see a
"mystic" topaz - there is no such thing in nature, it's white topaz coated with a metallic film
"pink" topaz - it is white topaz coated with a film
aquamarine - just try to find a naturally coloured aquamarine, virtually all you will see are an intense blue that results from being cooked
diamond - most stones of consequence these days have impurities lasered out
"green" diamond - some were produced in the 1920s by radiation; they are - and will remain - so toxic that they are kept in 1-inch-thick lead-lined safes
"coloured diamond" - heated to varying temperatures

i could fill the entire forum with specific incidences of alterations to gemstones - the alterations are costly and would not be done if the altered stones could not be sold at a profit.

as for the amethysts: naturally deep purple amethysts are rare and costly. everyone wants a deep purple amethyst, not a medium or pale one, so it is economically advantageous to cook the stones because they can be sold for a higher price. unless people stop buying altered stones these practices will go on. and don't think that "consumer education" will put a damper on the demand for intensely coloured stones; most people do not care that their stones have had 'cosmetic' work done on them.
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byron mac donald
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Postby byron mac donald » Sat Mar 22, 2008 3:29 am

K- (your name is to hard to write often, so for me it is "K"- okay?)

This is to bad that people view gems in this light, they may as well own paste. How can you tell if a gem has been cooked, can you tell by looking at the layers of amethyst, and if so do the layers look lighter than the color of the total stone?

Regards- Byron
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Doos
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Postby Doos » Sat Mar 22, 2008 1:40 pm

can you tell by looking at the layers of amethyst

Hi,

Although this is beyond this forum's topic, you can not differentiate natural from heated amethysts by looking at the enantiomorphism (to use a fancy term to indicate left- or right handedness of quartz) through colour zoning. Below the conversion temp. all quartz will show this. Some as left handed, some as right handed .. most as a mixture. Even modern synthetics may show this and you will need to know exactly what you are doing to make such a call.
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admin
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Postby admin » Sat Mar 22, 2008 2:24 pm

For those of you interested in gemology, Doos' website is a must visit.
http://gemologyproject.com/
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