Joined: Fri Jun 25, 2010 12:04 am Posts: 256 Location: Idaho
Howdy, Folks!
A client brought in a large gem her husband (since deceased) gave to her, no idea what it is.
RI OTL, moderate dispersion.
Moderately doubly refractive (facet lines doubled when viewed thru stone), along the lines of peridot for intensity.
Does not show dichroism - strange!
Gem shows damage where it has been dropped, more what you would see on a soft to mid hardness stone.
Perhaps of more help for some, the spectrum (diffraction) shows a strong wide band in the green, and strong double lines in red, plus a faint band in yellow.
A couple negative crystal inclusions, plus a zone of aligned silky needle blades.
From gem cutting experience, this looks like sphalerite, zincite, scheelite - some of the other softer collector gems but our GIA ID book doesn't go there. Has the brightness and color like an orange CZ (but DR). Has density similar to topaz...
Someone took the time to do a decent barion cut on it, but struggled with finer meets and the finish in some areas. Not some commercial cutting job.
12.14 x 10.18 x 7.84 (deep)mm, 12.30 ct
Sorry about the sparse facts, but it is trying to ring a bell in my memory, wondered if anyone else might find it familiar...
Attachments:
Yanke stone.jpg [ 72.61 KiB | Viewed 1755 times ]
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Doubling of back facets with sphene looks about the same.
If we can trust that the SG is close to topaz (3.4-3.6), zircon is too high (4.6–4.7) Sphene's SG is 3.4 to 3.6
Spectra sounds about right for some forms of Zircon.
I am not sure where he got his density estimation. When I plug his dimensions into my weight estimation formulas Topaz comes out under 9 carats. Zircon comes out very close to his weight in the 12 carat range.
Zircon still seems to be the likely answer to me at this point.
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