Tremolite - Ca₂Mg₅Si₈O₂₂(OH)₂

Habit: White, gray or lavender to pink. Elongated, stout prismatic or flattened bladed crystals; also fibrous, granular or columnar aggregates. Vitreous luster; transparent to translucent. White streak.

Environment: Formed by contact metamorphism of calcium-magnesium siliceous sediments. Occurs in greenschist facies metamorphic rocks derived from ultramafic or magnesium carbonate rocks.

Etymology: From its occurrence in the Tremola Valley (Val Tremola), Central St. Gotthard Massif, Switzerland.