Portal:Minerals/Did you know/2

... that Treak Cliff Cavern (pictured) is one of only two remaining active sources of the ornamental mineral Blue John?
...that chalcocite, a profitable and desirable kind of copper ore, was particularly plentiful in the now-depleted copper mines of Cornwall, England and Bristol, Connecticut?
... that Gloria J. Romero is leading a campaign in the California Legislature to remove serpentine as the official state rock because it is a source of cancer-causing asbestos?
... that the mineral abelsonite probably formed from chlorophyll and is the only known crystalline geoporphyrin?