a green to black mineral of the amphibole group; consists of silicates of calcium and sodium and magnesium and iron
{i} (Geology) variety of igneous rock, common dark-colored silicate mineral from the amphibole group; amphibole, any of several varieties of ferromagnesian silicate minerals
A black prismatic rock-forming mineral, the most common of the amphibole group It has a variable composition consisting of chiefly sodium, iron, magnesium, aluminum, and silica
It belongs to the aluminous division of the species, and is also characterized by its containing considerable iron
Any of a subgroup of amphibole minerals that are calcium-iron-magnesium-rich and monoclinic in crystal structure. Hornblende, whose generalized chemical formula is (Ca,Na)2(Mg,Fe,Al)5(Al,Si)8O22(OH)2, occurs widely in metamorphic and igneous rocks. Common hornblende is dark green to black in colour and usually found in middle-grade metamorphic rocks (formed under medium conditions of temperature and pressure). Such metamorphic rocks with abundant hornblende are called amphibolites