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first post, chrome green gems.

As I understood it the chelsea filter only distinguishes the presence or absence of chromium. The absence of chromium in some green tourmaline does not indicate that chromium is not a chromophore in chrome tourmaline. As "chrome tourmaline" is generally said to have chrome and/or vanadium , much the was emeralds from different localities are all emeralds regardless whether they are green by chromium or vanadium.

"Chromdravite (Chrome Tourmaline)

The name "chrome tourmaline" is somewhat of a misnomer, as many chrome dravite tourmalines can also have a predominance of vanadium, and dravite colored primarily by vanadium can have the same green color as dravite colored by chromium. Although the presence of chromium in "chrome tourmaline" does make it appear red when observed through a Chelsea filter (also used to evaluate emerald), this test cannot distinguish between vanadium dravite and green elbaite which is colored by iron (Fe). Therefore, a Chelsea filter is only useful in determining the presence of chromium, and not in distinguishing between mineral species."
- http://www.allaboutgemstones.com/gemstones_tourmaline.html

and this from dept. of geology, U of Texas, " Chrome tourmaline is a name of fairly recent vintage used for African (Namibia, Tanzania) material that has an outstanding, bright, vivid green color, resembling fine emerald. As the name suggests, the chromophore in this variety is principally Cr, but also probably involves vanadium. The source of color in other varieties is less clear and is probably complex; not all stones of a given color contain the same chromophores. In general, most colors can be attributed to Fe of valence +2, +3 or both, and/or Mn. Finally, several authors suggest dropping the somewhat antiquated, color-specific names in favor of simple color adjectives, e.g. green tourmaline, blue tourmaline. I agree; the names given above should serve for reference only."
- http://www.geo.utexas.edu/courses/347k/redesign/gem_notes/tourmaline/tourm_main.htm
 
I think if you guys like learning about this stuff, you should possibly try to get a subscription to Journal of Gemmology, along with publications from the major gem labs. Here is a quote DIRECTLY from the GIA (GG) course material:

For a long time it was believed that the two stones (chrome tourmaline and emerald) shared the same coloring agent - chromium. But, as with Brazilian emerald, gemologists later determined that most of these tourmalines are actually colored by traces of vanadium

Also, Halvorsen & Jensen, Journal of Gemmology, Vol. 25, No. 5 suggest that it is likely that stones from the Umba Valley are chrome-bearing (ie - coloured by both like LD said), but that this is a distinct characteristic of those samples and NOT characteristic of ALL so-called chrome tourmaline.

Furthermore, the idea that the Chelsea filter is selective for a single chromophore requires a misunderstanding of the technology. Filters block certain regions of the spectrum. The Chelsea filter provides a HUGE region of red spectrum for transmission. It is not selective for chromium in many many cases.
 
I'm sure this would be a lively discussion, and you are welcome and encouraged to open a thread for your subject. This thread is really about finding a stone for Agnes that is a color she likes and affordable.
Agnes there is a 1.75 ct CHROME TOURMALINE near the bottom of this page that is bright deep green and a real sweet price!

http://www.djraregems.com/finegems.html
 
Thresh,
I know that there are several different filters on the market to determine chromophores, synthetics and the like. Please start a thread on it. I would find it very interesting.
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me too
 
Date: 4/28/2010 10:43:21 AM
Author: Agnesg
Hello Sal, the vendor's pict is not as attractive as the photos you took. Your chrome tourmaline is a brighter green. The multicolor tourmaline http://www.multicolour.com/detail/?/details/single/chrome_tourmaline/ych119aa/&930512007
Click to expand...
My opinion of the photo of the stone is that I think it will be very dark IRL. You have to be very careful of chrome, or any tourmaline, being too dark in tone where it has too much blackout. I also don't see that as a bright saturated green at all. It's difficult to find very good colored chrome green tourmalines, and green doesn't photograph well either.

I think you should do a google search on chrome tourmaline and even tsavorite (which can look a lot like chrome tourmaline in color) and see many different hues and tones.

Here is what I consider to be a nice chrome tourmaline color with a very pure green hue and a medium dark tone (which is what I think you want by what you're picking out). It's not cut very well, but the body color is more saturated than the MC.com one you picked out, which looks to be more on the olive side.

http://4.bp.blogspot.com/_8Wwg8f9v0xg/RqufoYXdVaI/AAAAAAAAACE/4_JwfF3e3Mg/s1600-h/chrome_tourmaline.jpg

Also know that if you're looking for darker toned stones, it will be difficult to find a gem that's highly saturated. Dark tone and high saturation are rare in nature, and come at a higher price in my experience and from what I've seen.
 
This is a real useful forum, full of generous individuals. Thanks once again.
 
HI Agnesg! I am a newbie too! It will take some time and luck to find a stone you like. The precision cut stones will cost quite a bit more. You can check out some ebay seller with positive feedback if you wanna get a bigger bling with slightly less $$. But well, I guess you will need to compromise with occasional, ''not as perfect'' cut and polish. I believe you have contacted odysseygems but to no avail, maybe you can take a look at vvs1gems too.
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Good luck!
 
agnes, vvs1gems is one of Tan''s stores on ebay. Many of us have bought from him this was and still had all the services he would normally give including no questions return. Here is the webaddress of his ebay store: http://stores.ebay.com/vvs1gem__W0QQ_dmdZ1QQ_sacatZvvs1gemQQ_scZ1QQ_sidZ878076206QQ_stickyZ1QQ_trksidZp4634Q2ec0Q2em14QQ_vcZ1?_sop=1&_sc=1
 
AGnes, for the money this is a particularly nice chrome tourmaline in a quite elegant cut.

http://www.thegemtrader.com/Feb%2009%20CTourm%20Page.htm
 
Date: 4/29/2010 10:39:03 PM
Author: VapidLapid
AGnes, for the money this is a particularly nice chrome tourmaline in a quite elegant cut.


http://www.thegemtrader.com/Feb%2009%20CTourm%20Page.htm
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Thank you very much. VapidLapid you are one helpful soul..

There is only one sad Chrome Tourmaline in vvs1 website..Tan from odyssey, gemburi,vvs1 is not able to cut another so are the 3 cutters I had contacted. The gem traders' tourmaline is the color I would like to get..pure green..the shape is not..will not fit a ring. Just saw the other post, the chrome tourmaline on white diamond is a beauty..gemfix , oval Chrome Tourmaline should be my best bet.. at least for now
 
Be patient; gemstones do not come out of the ground when ordered. Keep looking and waiting until the right one comes along.
 
Date: 5/2/2010 12:29:55 PM
Author: Agnesg
The website does provide some help, thank you. I saw this green tourm http://www.customgemstones.com/TOURMALINE/to1300.html. Is it looking close to a chrome torm? what is oyo? is that the place of origin?
Click to expand...
I believe that it is the place of origin. That cutter (Dan) cuts very nicely and another PSer has a Stunning Oyo green tourm that he cut. It looks a bit dark to me in the cutter''s photo maybe ask him if it''s lighter than the photo? Dan is very easy to work with in my experience. Good Luck!
 
Is the green as intense as a chrome? This is not described as a chrome. Thank you I will get in touch with the cutter.
 
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