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I don’t know much about gems so I tried to upload pictures in different lighting.

The corundum pic Pictured with it was scratched by this stone.

I can’t tell if the corundum scratches this stone. It doesn’t look like it to me.

It was found in the Deposit Dan active volcano.

  • $\begingroup$ Is the 4th photo taken under uv (black light)? This could help determine what it is. Also, where is Deposit Dan active volcano? $\endgroup$ – user11318 Dec 1 '17 at 2:15
  • $\begingroup$ That should read, an active volcano. That photo was taken under a black uv light long wave. $\endgroup$ – user11321 Dec 1 '17 at 11:13

I believe it’s a portion on an amethyst geode.

amethyst geode

  • $\begingroup$ From a scratch test I agree that it should be relatively hard. Also, lack of cleavage planes and the growth lines suggest it's amethyst and not fluorite. I cannot think of any other similar mineral harder than amethyst (even including very expensive ones). $\endgroup$ – Gabija Dec 3 '17 at 11:13
  • $\begingroup$ I agree amethyst. Geode fragment from the lines and banding. I'd assume that 4th picture has glow from UV light reflecting off surface, not fluorescence of the rock itself. Also when scratched on corundum (Mohs hardness 9) quartz (Mohs hardness 7) would leave white line of quartz powder. So is the scratch really in the corundum or is there just white dust trail on the corundum? Diamond (Mohs hardness 10) is about the only thing that would really scratch corundum. $\endgroup$ – MaxW Dec 3 '17 at 23:47

You may want to take a look at fluorite. What's throwing me off is that you say this specimen scratches corundum? Corundum is a 9 on the Mohs scale and fluorite is only a 4. If you are unsure of this you could try scratching this rock with a steel pocket knife. Since the steel knife is ~6 on the hardness scale it should scratch this rock if it's fluorite. If not you can rule out fluorite. Additionally, fluorite fluoresces (glows) under uv (black light). Here is a link to more information on fluorite and the source of the image below.

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  • $\begingroup$ I did read up on fluorite and amethyst, as those were the to most common possible identification offered. It has also been most recently identified as a corundum crystal. I purchased a corundum to do a scratch test. The corundum when used to scratch this stone, shows evidence on the surface of the stone with a residue dust of sorts. When I remove this dust with my finger, I can’t see a scratch. However, when I use this stone to scratch the corundum, I clearly see a scratch. Do the results of this scratch test not eliminate fluorite and amethyst? $\endgroup$ – user11321 Dec 1 '17 at 12:59
  • $\begingroup$ It sounds like your scratch test eliminates fluorite and amethyst. $\endgroup$ – user11318 Dec 2 '17 at 1:52

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