Tremolite: Gemstones Information

Tremolite, Ca2(Mg,Fe2)5Si8O22(OH)2, is a member of the amphibolemineral group in which it forms a series with actinolite and with ferro actinolite. Stout elongated crystals of the monoclinic system are  typical as are fibrous, granular or columnar aggregates. There is a perfect cleavage in one direction; the hardness is 5–6 and the SG 2.99–3.03. The colour is grey, green or lavender to pink and the RI or the alpha, beta and gamma rays is 1.605–1.613, 1.616–1.624 and 1.630–1.636, biaxial negative with birefringence 0.027. The transparent pink variety hexagonite shows pleochroic colours, bluish-red to deep reddish violet. The name nephrite is not now used for a valid mineral species (see Chapter 20). The best Tremolite, Ca2(Mg,Fe2)5Si8O22(OH)2, is a member of the amphibole mineral group in which it forms a series with actinolite and with ferro actinolite. Stout elongated crystals of the monoclinic system are typical as are fibrous, granular or columnar aggregates. There is a perfect cleavage in one direction; the hardness is 5–6 and the SG 2.99–3.03. The colour is grey, green or lavender to pink and the RI or the alpha, beta and gamma rays is 1.605–1.613, 1.616–1.624 and 1.630–1.636, biaxial negative with birefringence 0.027. The transparent pink variety hexagonite shows pleochroic colours, bluish-red to deep reddish violet. The name nephrite is not now used for a valid mineral species (see Chapter 20). The best