ferrohornblende

Ferrohornblende is a mineral belonging to the amphibole group, specifically a member of the hornblende subgroup. It is a complex silicate mineral with the general chemical formula roughly approximating (Ca,Na)2-3(Fe,Mg,Al)5(Si,Al)8O22(OH,F)2. The name "ferrohornblende" itself indicates a high iron content, differentiating it from other amphiboles where magnesium might be more dominant. It typically forms in igneous and metamorphic rocks, often appearing as dark-colored prismatic or acicular crystals.

The color of ferrohornblende can range from dark green to black, and it possesses a vitreous luster. It crystallizes in the monoclinic system and exhibits cleavage in two directions, usually at angles of about 56 and 124 degrees. Ferrohornblende is generally considered a common accessory mineral in a variety of rock types including gabbros, diorites, andesites, and schists. Its presence and composition can provide clues about the geological conditions under which the host rock formed, such as temperature, pressure, and the availability of certain elements like iron and magnesium. While not typically mined for any specific economic purpose, its occurrence is significant for petrological studies.