These were found, buried, in Southern California. I did the acid test, not a form of Calcite. Thinking it's possibly Spodumene? It's brittle, dark smoky green to yellow in color, translucent in some areas, and flat in some areas, some pieces have irridecent flashes.
Joined: Sat Sep 29, 2007 8:14 pm Posts: 1383 Location: Royal Oak, Michigan US
deeni wrote:
no one has any ideas? thoughts? opinions?
Hi Deeni, working in the field has me become even more cautious as to relating my opinion when I don't have enough 'facts'. What we know so far, is a location, and photos showing some possibilities. Since you have the crystals in hand, it would be really helpful to acquire a specific gravity reading at the very least, and hopefully get at least one surface polished so a refractive index reading can be rendered.
Then, it may be possible to isolate some possibilities.
I am sorry to report, that as a general rule, gemologists are not risk takers when it comes to laying out their opinions.
Actually, these specimens do show quite a few characteristic features. Just from looking at the pictures, it looks like it is gypsum: I can see pearly lustre, flaky habit, longitudinal cleavage, scratched surface (low hardness), let's also add gypsum is often found buried in the ground as was reported. Of course some testing would be suitable so to confirm it: gypsum cannot scratch your finger nail but gypsum can be scratched with the finger nail.
Never underestimate the many clues you can get through a careful visual observation of both external and internal characteristics (first with the naked eye, and then with the loupe). This is especially true for rough minerals even more than for cut stones (notably, crystal shapes, cleavage and fracture are important). Also very helpful for identification of minerals are paragenesis (i.e. associated minerals), geological setting, and exact locality of origin. Of course, the more minerals you see the easier it gets.
If you take a very thin plate cleaved from a crystall, can you bend it a little?
Another test for gypsum would be to put a small piece in a test tube and heat it from below. if water condenses in the cooler parts of the test tube this would also be a sign for the mineral in question beeing gypsum (gypsum contains water).
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