calcite - hot pink fluorescent and phosphorescent calcite cleavage rhomb from the Challenger Cave system, Nuevo Leon, Mexico ceasing in World War I

ceasing in World War I and taking some time to resume

Often they are completely mineral-filled

If treated with  a combination of sulfuric and phosphoric acids

no coins - some phosphorescence

Piedras Verdes District

calcite - hot pink fluorescent and phosphorescent calcite cleavage rhomb from the Challenger Cave system, Nuevo Leon, Mexico ceasing in World War ICalcite, CaCO3, is an extremely common rock forming mineral. In pegmatites it forms large masses and it makes up some limestones almost entirely. It has a large variety of crystal forms, but these do not include the rhombus shaped pieces that are sold as calcite crystals. The rhombs are produced by cleaving calcite in three directions between rows of atoms. When calcite is free of impurities and is optically clear, it exhibits double refraction. When