These are specimens of zincite, or zinc oxide, which grew in a refinery smokestack in Poland. Apparently this material was accidentally produced in an old Soviet-era refinery which had very dirty, zinc-rich exhaust--as the gases cooled the zinc oxide crystallized out, slowly building up transparent gemmy crystals in a variety of colors and forms. Some are even fluorescent, in part or in whole.
Specimens like this are called 'anthropogenic'--not intentionally lab created but still made by human activity.
I remember this material being relatively abundant at gem shows back in the 90s, but it has become much scarcer as more and more disappeared into collections. I have been trying to find some for a while now but was finding it rare and, when found, expensive. This year we were lucky to finally find some reasonably-priced specimens at the Tucson gem show.
Each specimen is lettered and individually photographed.
