Actinolite is a mineral that belongs to the amphibole group, which are silicate minerals containing iron, magnesium, and calcium. It has a chemical formula of Ca2(Mg,Fe)5Si8O22(OH)2, and its name is derived from the Greek words "aktis" meaning "ray" and "lithos" meaning "stone" due to its fibrous or needle-like crystal habit.
Actinolite typically occurs as fine, green to dark green prismatic crystals, but it can also appear as fibrous aggregates or as a component of metamorphic rocks. It has a Mohs hardness of 5.5-6, making it relatively hard, and a specific gravity ranging from 2.9 to 3.4.
This mineral is commonly found in metamorphic rocks formed under high temperatures and pressures, such as schists, gneisses, and greenstones. It often occurs alongside other minerals like chlorite, epidote, and quartz. Actinolite is also found in some igneous rocks, including ultramafic rocks like serpentinite.
In terms of its physical properties, actinolite has a strong, fibrous habit, and when fibrous, it can exhibit a silky luster. It typically has good cleavage in two directions, which distinguishes it from related minerals such as hornblende. Actinolite is not usually transparent, but thin, elongated crystals may display a translucent to transparent appearance.
In geological and industrial settings, actinolite may have varying applications. For instance, it can serve as a guide in determining rock type and metamorphic conditions. Additionally, due to its fibrous nature, actinolite has been used to manufacture asbestos, although its
