Tremolite
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Tremolite is a member of the amphibole group of silicate minerals with composition: Ca₂Si₈O₂₂(OH)₂. Tremolite forms by metamorphism of sediments rich in dolomite and quartz. Tremolite forms a series with actinolite and ferro-actinolite. Wikipedia
2V angle: Measured: 86° to 88°
Birefringence: δ = 0.026
Cleavage: Perfect on, at 56° and 124°; partings on, and
Color: White, gray, lavender to pink, light green, light yellow
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal habit: Elongated prismatic, or flattened crystals; also as fibrous, granular or columnar aggregates
Crystal system: Monoclinic