Datolite

Datolite is a phyllo-borosilicate commonly forming as nodules in igneous rocks. Facet-grade material rarely yields gems larger than 10 carats, with most being significantly smaller. Colorless, transparent datolite gems can be found in several locations worldwide, but many come from Connecticut, Massachusetts, New Jersey, and Virginia. Copper-stained, opaque nodules from Michigan are typically fashioned into cabochons.