Topazolite Garnet

I am pretty sure it’s a zircon. Pretty though

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the spectra reminds me of the old “depression glass”… Pb-enriched. Check the R.I. leaded-glass is usually around 2.15… zircon is about 1.95 … and garnet should be less than 1.80.

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New spectra from a different spec
First shows yellow gem and a blue zircon (probably phony)
Second shows yellow gem and spessarite garnet (don’t have Andradite garnet)


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refractive index for garnet is 1.73 to 1.759 for Zircon it’s 1.93 to 1.98. Zircon is birefringent while garnet is not. I would vote for zircon with the others.

@StevenH26783 it was my understanding that some varieties of garnet can read above index (1.80)?

Some garnets can have RIs over 1.80. This includes garnets of the andradite variety which would include topazolite. This article contains a table that compares the RIs, colors, and spectra of some garnet species and blends.

thanks for the professional information… am I correcting in saying that andradite, grossular and uvaroite belong the ugrandite family of calcium garnets with Al, Fe, and Cr substitution for each other. Andradite would be the Fe3+ end member grossular being the Al+3 end member. None of them occur as a pure endmembers. I also have read that there’s some 2+ My question is how close to the andradite endmember is topazolite? some scholarly sources show limited divalent ion substitution with the pyralspite group. Mg+2 has an ionic radius that is too small. The transition metals following Ca+2 have similar sized radii…but ae not in the divalent site…I would also presume that a high Fe content would give a garnet a higher RI and SpG. Am I correct or not?.. or it it more complicated than that?.

Hi again I have picture of the yellow gem above a thin pencil line. Sorry for the poor quality I am having trouble with a new digital mic

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whatever you have is an attractive stone. Could be quite valuable if it can be definitively ID’s as topazolite. Good luck

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Just from the look, I would guess Sphene.

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Hi thanks for the response, even if it is a flawless 7 carat sphene I would be very happy. It has been kicking around my collection loose for a long time with no visible damage. I am snowbirding at present but I will check the stone with my very sensitive Geiger counter when I return home.
Thanks again

unless there’s a lot of thorium substituting for calcium in titanite, it might not be highly radioactive. titianite is mildly radioactive at best. what is the specific gravity?

I would look for doubling, if it doubles, it is most likely zircon.

Have you considered sphene (titanite)?

I agree with the people who said sphene (titanite). A little brighter light would help, as a clean, well cut sphene tends to disperse multi-color like a diamond. I have one in a pinky ring and people always comment on it and want to know what it is.

I think the high dispersion is more interesting than the R.I… garnet (even topazolite) does not have that high of dispersion… you have a real rainbow of colors coming out of the gem. Now… I have cut some “antique glass”… old Pb-glass that is exactly the same color and looks very similar (it is suppose to have a high RI value… I haven’t measure mine for same reason… my refractometer doesn’t go above about 1.80… but it does have the righ dispersion and the right brilliance. I you put it under a polariscope (or just between two sheets of polarized films… and it stays dark as you rotate… then it is probably antique glass … garnet would do the same as it is isometric… both sphene and zircon will “blink” light and dark every 90-degrees of rotation. That might help with the ID.

It’s either a yellow zircon (probably), sphene or sphalerite IMO. Is it doubly refractive? If so, definitely not a garnet, which is single.

This looks like Sphene to me. If it is sphene you are lucky to have such a large size. It’s beautiful.

Hello again and thanks for all your replies. I look carefully but I do not see any doubling so as someone mentioned do a specific gravity test so I did multiple times just using a three place balance and came up with 3.795 which maybe Andradite Garnet. I am not holding my breath yet but it looks exciting
Lou

Hello again I did some further test using my gem eye meter and tested three stones the garnet a zir on and the yellow stone. Yellow stones first zircon next then garnet.


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