Just tossing this out there, since there’s no RI or spectrum offered above, and this could be way off, but possibly low-type zircon? Metamict material? Natural radiation can break it down to being amorphous. I’ve had a few such gems, only as cabs if I recall correctly. Colour’s a good match (rich green) for what that’s worth and the look of the material from the bottom of the cab is similar to the first pic. (Can I attach pics to these messages? I can send a pic of one I have in stock).
Green zircon, usually from Sri Lanka, is not cubic but birefringent (orthorhombic class}, has a high SG and usually contains more than !% uranium impurity that is easily detected by a Geiger Counter, Because of its high radioactivity these green gems are usually cloudy when mined and are heated to anneal and cllarify them for the gemstone trade, The green color is reputedly due to the uranium but my research indicates that it is due to dispersed lead particles (as also seen in green plumban feldspar) and arising from radioactive decay of contained uranium in the zircon. Although it is not common practice now, such zircons should be sold with a warning notice from jewellery and gem merchants.
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Is “!%” meant to say “1%”? And I missed the part when he confirmed it was SR (oops). I explain to my clients the nature of the gem when presenting the jewellery to them. There’s a certain ‘visual hum’ to the gem (I can think of no other word) that I have not seen in other gems – any thoughts on that Ivan? I find them very intriguing. If I could find out how to attach a picture here I would show an example.
Thanks to all on this forum, your questions and suggestions are a big help. I’m sorry I hadn’t been able to login for a bit to give the
SG-2.49-2.53,
RI-1.50 SR ADR.
I’ll let you know when I know what I find out after Mass Spec. All I know is it makes a beautiful gemstone and my mom loves it. I certainly think natural glass is a good possibility except I wouldn’t expect the amount of brilliance this displays, from glass and what appears to me as crystalline structure, which I know very little about. I don’t really think we can know for sure without more info, so back to the lab I went.
Also having others analyzed which I know the provenance of, as I wish I could tell you for these samples of my great grandfather’s.
I believe just by looking at the rough and the cut gem that the stone may actually be Russian Chrome Diopside. Every Emerald wishes it had the clarity and color of Chrome Diopside. The gem is typically mined about 2 months out of the year due to permafrost in Siberia. I don’t believe it’s a moldavite due to the color, moldavite is more of a green olive color and has numerous bubbles in it. Moldavite came in a meteorite hence all the bubbles it naturally contains. The last guess would be demantiod garnet. With that said Russian Chrome Diopside is my best bet. Gl
Chrysophase is more turquoise- colour
Yes. I meant 1% uranium which is why green zircon needs heat treatment to clarify it. The uranium decay produces alpha particles which are actually helium nuclei. Bombardment from these and recoiling atoms within the crystal lattice cause what is called mectamitisation, which is essentially the breakdown of zircon into zirconia (zirconium oxide) and amorphous silica. On heating at above 800 degrees Celsius these breakdown products will recombine to zircon producing better transparency. The zircon however will still continue breaking down until the contained uranium completely decays to lead,
I am not aware of any “visual hum” due to radioactivity but I would strongly advise informing your clients of the fact that green zircon is radioactive because of its relatively high uranium content. The World Health Organisation has issued an occupational health standard for radioactivity in zircon sand as used for refractories. This does not apply to gem and especially green zircon but needs to be kept in mind in case customers may sue later.
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Thanks Ivan, Very interesting. Just to clarify my use of ‘visual hum’. Even as a professional writer I find it challenging sometimes to find the right words. I don’t want to suggest at all that the ‘hum’ is anything radioactive, I just mean that when I look inside these green zircons I find them mesmerizing but a bit of a different mesmerizing than I feel with other gems. In the same way that moonstones have a ‘hum’ from the adularescence as opposed to the sharper ‘twinkling’ of high RI gems, I find that these green zircons also draw me in in the same way (no, I’m not saying they have adularescence). They simply catch my eye in a different way. Perhaps being metamict, they are neither ‘here nor there’ but somewhere in between lattice and amorphous that intrigues my eye. Who knows! But wonderful material. Thanks Ivan. Again, anyone know how I can attach a picture?
Hello, Have you considered Chrome-diopside? The colour seems about right given my monitor settings. The best examples come from Siberia - what is the provenance of your stone? It is a really lovely green.
Thanks again everyone for the info. It really is an eye catching stone. Unfortunately I don’t know the provenance of this material, I know it would help. All I can say is it was collected a long time ago by an ancestor who knew way more about geology and mineralogy than I ever will.
Zircon is an interesting suggestion and I didn’t know that about the degradation process of them. I wondered then if that process might change the specific gravity? This is fairly light material and I think chrome diopside is very likely after seeing some of the inclusion patterns in other chrome diopside.
I’m waiting for ICP-MS results because I have to know before I feel confident in trying to sell, but this is all great stuff to know and I really appreciate all the interest and help with this.
The only sticking point for me would be the specific gravity- 2.5.
I wondered how much the specific gravity might vary, or be changed by the degradation process that Ivan mentioned?
No way Zircon SG can go that low. Could be very old glass
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the high calcium content rules out alkali feldspar, ie, microcline, albite, orthoclase. The absence of Mg and hi Ca also rules out peridot. Cafemic minerals such as clinopyroxene is a possibility… Arsenic would also be not present in peridot. garnet and other cubic minerals are singly refractive, but garnet has already been excluded by SpG. all others including quartz are double or triple refractive. Singly refractive doesn’t distinguish it from a glass. A higher magnification of the bubbles could help. If it’s all single phase, ie., gas or a void, glass would have to be considered. Liquid/gas or rarely liquid/solid/gas would point to a natural mineral. The solid phase would be a micro crystal. These types of inclusions occur in high pressure mineral crystals… the raw specimen looks like a low pressure non crystalline substance… a glass would be confirmed by a strong conchoidal fracture, but no fractures are visible in the specimen, In the absence of Cr, FeO would color glass green. As and Zr in percentage amounts constitute more than traces. That might point to a glassy synthetic. If this is a high Ca mineral, that would be strange other than lime glass… More chemical data, with Na, K, Mn, Ni, Cr, would be helpful.
all zircons contain some uranium. They are a geologist’s best friend as they are used to date rocks of very ancient origin. The uranium is sealed within the crystal structure of zircon and none gets in or out once the zircon is formed, making them time capsules…the dating of very old detrital zircons has pushed back the formation of the earth’s crust and plate tectonics 500 million years. Ur/Pb isotope ratios involving the decay of both U238 and U235, with Pb204 and 206 being endproducts of Ur decay… fission track counting are some of the methods used. That being said, I still have to agree wit end products being with royjohn… the rough looks amorphous and glassy more than crystalline. Singly refractive also applies to natural glasses like moldavite and not just to isometric/cubic system crystals…the Moh’s hardness of glass natural or otherwise would be less than their crystalline counterparts as glass has a disordered internal structure. the SpG is too light to be garnet which is much denser. Hardness is on the soft side… that would also exclude garnet as well as zircon. the presence of As and Zr in more than trace amounts would point towards a felsic composition of igneous origin… the high amount of Ca suggests glass, but man made glasses would not have hi Zr and As…
If you do send it out for ID, please let us all know what it comes back as. This one is as royjohn put it,
is a “head scratcher.”
Hello Steven. I think your question should be directed at Scott rather than myself.
Anyhow, the physical and optical info don’t fit chrome diopside which is a low value gemstone anyway. They also don’t match Hiddenite which attracts more $'s. My educated guess is that it is a natural or synthetic volcanic glass, perhaps left over from the Victorian era where such glasses were produced to imitate emerald.
I think it’s time to have this stone examined by a professional Everyone has contributed good ideas. definitive ID is something that I don’t think is possible without it being tested by a gemmologist with lab equipment. Thanks for the very interesting discussion…