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Pretty sure that was calcite - famous for double refraction.

You are correct. I misremembered.

Flourite was ... very fluorescent.

as it turns out, pure fluorite has no fluorescence, even though fluorescence is named for fluorite

Well, it has been a long time (like, 40 years), but I’m pretty sure I remember it being strongly fluorescent. It might have been impurities, though.

yeah, that's normal, which is why it's called fluorescence. pure natural minerals are very rare