What sort of rock is this one? the photo in questionenter image description here

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    $\begingroup$ it might be fluorspar,does it give off light if you heat it to 150-200C,or if you use uva light(blacklight). $\endgroup$ – trond hansen Oct 25 '18 at 4:47
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    $\begingroup$ Anything else you can add from this guide? Additional pictures taken under natural light (outside, no sun) would be good too. $\endgroup$ – Jan Doggen Oct 25 '18 at 8:34
  • $\begingroup$ I suggest checking it with both wavelengths of black light as Trond recommends that region of NJ has some very unique florescent minerals. The Franklin Mining museum has some minerals found nowhere else on earth. Also check harness that will help. $\endgroup$ – John Oct 25 '18 at 14:25

If the second picture is under a black light, its most definite an indiction that the minerial is fluorite which fluoresce blue and violet. This and the moh hardness test should tell you more. Remember that a steel file has a hardness of 6.5 and fluorite a 4 so the file will scratch the mineral but not the other way. I believe that fluorite has a slight double defraction as well but this isnt always a good indicator since some amythest can appear cloudy. The hardness test should tell you.


While the photo is not the clearest... the colour, and what I am interpreting as conchoidal fracture, is certainly indicative of Amethyst, a variant of Quartz.

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    $\begingroup$ And you can distinguish it from Fluorite with a hardness test. $\endgroup$ – person27 Oct 27 '18 at 21:50

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