The chemical composition of tremolite is Ca2(Mg,Fe)5Si8O22(OH)2. The crystals are long and bladed, and crystal twinning is common. It is sometimes in the form of columnar, fibrous, feathery (radiating), blocky or granular aggregates. It can be colourless, white, grey, green, pink or brown. It has transparent to translucent diaphaneity, a vitreous or silky lustre, a specific gravity of 2.90–3.20 and a Mohs hardness of 5–6. It belongs to the same subfamily as actinolite. It is mainly found in contact-metamorphosed limestone and dolomite and sometimes in serpentinite. Tremolite is a heat and electric insulator and is resistant to acids, alkalinity, and corrosion, so it has a wide range of usages.