Hello folks, Today’s lengthy and informative post regarding the
trading practises of “Thaigem” brings up a more personal question. I
have some some brilliantly green tourmaline rough from Maine which has
been described to me as chrome tourmaline. But how can I tell for
sure? Is there a reliable, easy, test? Chelsea filter perhaps? Or if
there is not a reliable and easy test, what test method is used to
distinguish the two?
Cheers & thanks,
Hans Durstling
Moncton, Canada
My rule of thumb is that the Chrome Tourmaline doesn’t go black on
the C Axis. However this doesn’t mean that if a stone doesn’t go
black on the C, axis that is a chrome tourmaline.
A test with a spectrometer is about the only way outside of a lab to
detect the chrome content that I know of…
Don
Hans:
I think you are going to get different answers on this. I thought I
would find mention of chromium lines in the spectrum of chrome
tourmaline vs none in other green tourmaline. Instead, Liddicoat
doesn’t mention specific tests for chrome tourmaline and my GIA Gem
Reference Guide indicates that chrome tourmaline is a varietal name
for a “fine, intense green tourmaline” and further states that this
color is often due to vanadium rather than chromium, so I guess it is
a color issue.
I would say that if you’re buying, it’s not chrome, but if you’re
selling, it is.
HTH,
Roy
I have not heard of any verified strikes of chrome tourmaline from
any lo cality outside East Africa. Although there is some controversy
over this method, chrome tourmaline will normally show up as pink
under the chelse a filter.
If memory serves I once spoke with a Maine dealer who claimed to have
Mai ne chrome that showed up reddish under the filter.
RWW
If you have maine tourmaline…that is something more specific than a
chrome or a standard green… Maine tourmalines have a UNIQUE
color…(especially the greens) most of the time they have a
saturation of blue mixed in the green, giving them a very bright, but
warm color. though I am sure people refer to these as “greens” I
think that the maine tourmalines are truely different from the
standard brazilian green. You may want to read about maine tourmalines
in the new lapidary journal… One of the maine mines is the Plumbago
Mine…and there is a great exhibit at Harvard University featuring
the Hamlin necklace, Maine Tourmalines and a beautiful exhibit of
John Marshall Jr. + Sr.'s collection of tourmaline. (who donated a
large majority of specimens, and also some of the money to show the
exhibit)
I think that there’s an absorption test to see if the light spectrum
is absorbed in the Chrome signature range.
This is the way you tell ruby apart from red sapphire. I have some
red sapphires and never even knew they existed before, and they are
not rubies, though they are as red.
Africagems has a beautiful selection of tourmalines. Both Chrome and
Green ones are here if you want to have a look. I’m not sure if
there’s a standard difference in color, but I was previously of the
opinion that the chromes tended to be darker green in color. I’m not
sure if that’s correct or not.
http://www.africagems.com/inventory/tourmaline/tourm_index.html
I’m intriged by Darcy’s comment about Red Sapphire vs ruby. Can any
one shed more light on this subject?
Cheers from Don at The Charles Belle Studio in SOFL where its still a
dry rainy season and simple elegance IS fine jewelry!
@coralnut
Darcy, Ruby is red corundum. All other colors of corundum are
sapphire. Corundum is aluminum oxide. In the case of ruby, a
substitution of a Chromium ion for aluminum in the amount of 1 to 3
percent accounts for the red color. Iron and other impurities in
addition to the Cr will modify the pure red causing the stone to be
purplish, brownish, etc. but nothing else will cause it to be red.
Jerry in Kodiak
I'm intriged by Darcy's comment about Red Sapphire vs ruby. Can any one shed more light on this subject?
I’ve forgotten what the original context was, but “red sapphire” is
red corundum which IS ruby. As far as I know, there is no such animal
as red sapphire that is distinguishable from ruby. Now red beryl (aka
“red emerald”), that’s another thing altogether.
Beth
Coralnut, I could not find the reference you talked about concerning
red sapphire vs. ruby. Red corundum is ruby all other corundu m is
sapphire. Pink sapphire is a desaturated red, and, at some point, it
is difficult to draw the line between saturate d pink and lighter red.
Trust me, when you’re a seller it’s ruby, when you’re a buyer is dark
pink sapphire!!
Wayne Emery
Hi all; Excuse me for butting in but. . .I’ve always thought that any
corundum that is truly red is considered ruby, and if it’s pink, or
purplish red (beyond a debatable shade of bluish), it considered
saphire. Could we be talking about “red emerald” here? There is a
form of beryl that is definitely red and is often referred to as red
emerald. It’s really quite beautiful. Pricewise, I don’t know how it
goes.
David L. Huffman
Hmm. Well the things I have are definitely red… they look like
african rubies, rather than Burmese color.
If any gemologist on the list is interested in solving the riddle,
I’ll send you one of these in the mail for examination :-).
I was told they were red sapphire, no chromium, so technically not
rubies, when I bought them. They’re small stones, about 4mm round cut.
I’m no gemologist, nor do I have the equipment to determine what
exactly is going on…
I’d love to hear the results of an exam though! Any takers?
Red sapphire was a trade term developed by marketers of African
rubies that tended to be darker and slightly brownish in color than
what is normally coming out of other locations. We have bought and
sold a lot of this material. When it first came onto the market we
sent some to the GIA and it all came back as ruby. We primarily sent
it to them as we wanted to know if the red was red enough to be
classified as ruby. Red sapphire, after all, is ruby. It is just
simply the power of marketing that has made it into something else.
Daniel R. Spirer, G.G.
Spirer Somes Jewelers
1794 Massachusetts Ave
Cambridge, MA 02140
617-491-6000
@spirersomes
www.spirersomes.com
That’s interesting. I was told that sapphires come in all colors
except red and if you have a red one in that family then it is a ruby
not a sapphire. Is there a gemologist in the group? What is the
answer?
Thanks, Donna
Red emerald is also a trade term coined by Ray from Equitorian
Imports. It refers to red beryl, which, of course, is not emerald
any more than aquamarine is blue emerald. Incidentally, Equitorian is
a great source for emeralds.
Daniel R. Spirer, G.G.
That's interesting. I was told that sapphires come in all colors except red and if you have a red one in that family then it is a ruby not a sapphire. Is there a gemologist in the group? What is the answer?
It’s CORUNDUM that comes in all colors. When it’s red it’s called
ruby; when it’s anything else it’s called sapphire. Ruby and sapphire
are mineralogically the same stone with the exception of trace
elements (like chromium) that give them their colors.
Beth
Sapphire and ruby come from the same family, corundum. I have seen
pink and red corundum which was not of sufficient shade to be called
ruby but, that is all up to the seller’s spin. The rule of thumb I
learned is corundum comes in many (all?) colors if it is red it can be
called ruby (what is red?) and if any other color it is sapphire. Blue
(again dark blue, cornflower blue???) is the most popular sapphire
color and best marketed. Most by huge percent of corundum is heat
treated to bring up the blue colors. Sam, Tucson
Donna, Darcy, et al I am a GG and have an MS in Mineralogy. Most of
my earlier life was spent traveling, buying rough, cutting it and
sellin g it. I no longer cut but maintain my avid interest in colored
stones. Red corundum is ruby, period. Any other color, including weak
red saturation, which is pink, is sapphire. Darcy, I’d be glad to
check the refractive index of your stone (s). Some samll synthetics
(like the size you are talking about) might occasionally be very
difficult to very as such, so you might consider sending the stone to
Professional Gem Sciences, an identification and grading laboratory in
Chicago. The owners, Tom and Miryam Tashey are the best in the bu
siness, and former operators of European Gemologocal Laboratory, Los
Angeles. Then you’ll KNOW what you have.
Wayne Emery
I’m a FGA (Fellow of the Gemological Institute of Great Britain - two
years hard work and six nasty exams!)
My understanding is that if you can see the chrome absorption lines
under the spectroscope (a strong doublet at 6942 and 6928 angstrom,
moderate at 6590, a broad one at 4765 to 4750 and another at 4685)
then the stone contains chrome and is classified as a ruby. Anything
else and its a sapphire.
Tony Konrath
Gold and Stone
www.goldandstone.com
tony@goldandstone.com
Besides Ruby, there is also an orange colored Corundum with a pinkish
hue that has it’s own name, Padparadscha. One of my text books states
that it is a Sinhalese word meaning “lotus blossom”.
Charles Heick
Cincinnati, Ohio