A Ruby by any other name is still a Corundum. Corundum (Kauruntaka or
alpha-alumina) is hexagonal Aluminum Oxide. Pure corundum is colorless
and transparent. When colored by impurities, it is given a varietal
name. Non-gem varieties come in all colors and are called “ordinary
corundum”, ( can also be named adamantine spar and Armenian stone.) If
a corundum crystal is gemmy, then its color plays a significant role
in giving the piece a variety name. For example, a deep, blood red
stone is called…a ruby. Orange varieties are called Padparadschah,
Oriental emeralds are green, Oriental topaz are yellow, Oriental
amethyst are purple. These and other color varieties have been known
in the past as Karund, Adamas Siderites, Corinindum, Corinendum,
Demantspath, Spath Adamantin, Corindon, Corindon Harmophane, Corindon
Adamantin. And the blue varieties are known as: Sapphire, (originally
applied to Lazurite), Hyacinthos, Asteria, Jacut, Lychnis
Carbunculus, Telesie, Corindon Hyalin, Salamstein, Saphir, and
Sapphirus. The black varieties generally fall into the Emery slot.
However, Emery is really a mixture of corundum, magnetite, hematite,
and spinel. Some names for the “black sapphires” aRe: Schmirgel,
Armenian Whetstone, Naxium, Naxium ex Armenia, Pyrites virus, Smyris,
Smergel, Smiris ferrea, Smirgel, Schmirgel, Emeril, Corindon
granuleux, and Taosite. I am not clear on the varieties called
Chlor-sapphire,and Barklyite. Nor am I sure if Alexandrite-sapphire is
appropriate for the color change varieties. Speaking of color change,
if you heat a ruby, it first turns green, then white. The colors
revert as the stone cools. So, I suppose to call a pigeon-blood red
stone a ruby is correct at room temperature, but at 1300 degrees
centigrade, it should be called a hot sapphire. Cool it too quickly
and it would then be called ordinary corundum. It will be interesting
to see what new names the television shopping channels will give to
the colored varities of gemmy corundum in the future. Will Estavillo
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.
I just came into possession of a number of these stones. After a lot
of research and consulting experts, I believe the iron content is the
key. The ones I have resemble the old iron-rich Thai ruby that was
all over the market during the 1970s and 80s, although I think they
contained some chromium. I believe the red Songea material is called
“sapphire” because it does not contain chromium and is mostly colored
by iron, like most garnets except chrome pyropes. According to
Liddicoat, ruby, by definition, is colored by chromium, and its
presence can be determined by spectroscopic examination. But all red
corundums were traditionally considered “ruby,” along with red
spinels and probably fine red garnets.
The Songea and Thai reds are hard to distinguish (by color) from the
better qualities of garnet. Both can contain significant tones of
brown, typical of Fe as a coloring agent. A quick check for
double-refraction separates corundum from garnet quickly. While the
red African corundum can cut some very nice stones they don’t compare
at all with the lighter stop-light red tones of fine chromium ruby.
It’s interesting that the same situation applies to some iron-rich
beryls whose darkish green coloration is caused by iron and not
chromium. These stones and the green beryls colored by vanadium are
still disputed by some as being “emerald” although Tiffany & Co. long
ago accepted the vanadium-rich stones from Africa as real emerald.
Ultimately, these issues should be decided by the market, no matter
what labs may say. I’ve done enough business with labs over the
years to know there’s a whole lot of disagreement between “experts,”
and gemological trends come and go.
Rick Martin
MARTIN DESIGNS
Hello Darcy, First of all you must have it checked for RI, SG etc… to
see if it is really a corundum. It may be a tourmaline, a garnet,
glass imitating corundum, etc. etc. Red corundum is ruby. As coloring
element ruby has cromium in it . The absorption lines in the spectrum
is on the red end as fine lines. Most rubies will fluoresce under UV
light. In GIA’s “colourstone grading” courses I have learned that the
tone and saturation makes the difference on some red and pink varities
of Corundum and between green beryl and emerald. (also emerald have
chromium as colouring element and most green beryls have vanadium) For
example; vstrbG-3-3 means; light(tone) dull(saturation), very strong
bluish green (body colour) is green beryl. Because for emerald if the
saturation is dull, the tone starts from medium light. For green
beryl the best colour is medium light(tone), dull(saturation) slightly
yellowish green. This tone and saturation can be for emerald, but the
body colour is green then. And it is a low quality emerald colour. For
emerald best colour is medium (tone), strong (saturation) bluish green
(bodycolour). For ruby; best colour is medium dark(tone),
vivid(saturation), red(body colour). The pink saphire’s best colour is
medium light(tone), vivid (saturation), red-purple/purple-red(body
colour). There is a pink saphire which has red body colour. With
medium light (tone) vivid(saturation)at its best, or medium (tone),
dull(saturation) which is a low colour quality. Do you think these
explanations may help? Kind regards from Turkey, Oya Borahan
http://www.birdamlasu.com