Selenite in Chalcedony

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Sometimes I collect fluorescent rocks which surprise me once I get home in a really dark room. This is one of them. I have several pieces of gypsum from France and North Africa.

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But this rock out of Crawford, Nebraska tells the story of why I enjoy this hobby of fluorescent minerals so much.

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The orange fluorescence is the selenite gypsum crystal. The green comes from traces of uranium in the chalcedony/silicon dioxide. And the whitish blue? I'm not certain but it might be from calcium carbonate. This fluorescence is seen under shortwave ultraviolet light.

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