Ophicalcite

Ophicalcite, a crystalline limestone containing spots, veins, or interlaminations of serpentine, as in the so-called "serpentine-marble" of Ballynahinch and the "Eozoon" (q.v.) limestone of the Archaean rocks of Canada. Its exact mode of origin is obscure, the alteration of a magnesian limestone containing silica, and that of a limestone interpenetrated by contact-action with magnesian lava, having both been suggested.