Tremolite is a member of the amphibole group of silicate minerals with composition: Ca2Mg5Si8O22(OH)2. Tremolite forms by metamorphism of sediments rich in dolomite and quartz. Tremolite forms a series with actinolite. Pure magnesium tremolite is creamy white, but the color grades to dark green with increasing iron content.
It has a hardness on Mohs scale of 5 to 6. Nephrite, one of the two minerals of the gemstone jade, is a green variety of tremolite.
A fibrous variety of tremolite is used as asbestos. This material is toxic and inhaling the fibers can lead to asbestosis, lung cancer and mesothelioma.