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The mineral hornblende is a complex silicate which is an isomorphous mixture of three molecules; a calcium- iron- magnesium silicate, an aluminium-iron-magnesium silicate, and an iron-magnesium silicate. Manganese, titanium, and alkalis are sometimes present. Hornblende has a hardness of 5 - 6, a specific gravity of 2.9 - 3.4, and is colored green, greenish-brown, opaque, brown and black.

Hornblende is a common constituent of many igneous rocks such as granite, syenite, dioriteDiorite is a grey to dark grey intermediate intrusive igneous rock composed principally of plagioclase feldspar (typically andesine), hornblende, and/or pyroxene. Varieties deficient in hornblende and other dark minerals are called leucodiorite . It is of or gabbroGabbro is a dark, coarse-grained, intrusive igneous rock chemically equivalent to basalt. It is a plutonic rock, formed when molten magma is trapped beneath the Earth's surface and cools slowly into a hard, coarsely crystalline mass. It is dense, greenish, of gneissGneiss is a common and widely distributed rock type formed by high grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. Gneissic rocks are coarsely laminated and largely recrystallizedes and schistThe schists form a group of metamorphic rocks chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, etc. Quartz often occurs in drawn-out grains to such an extent that quartz schist is produced.s, and is the principal mineral of amphiboliteAmphibolite is a gouping of rocks composed mainly of amphibole (as hornblende) and plagioclase feldspars, with little or no quartz. It is typically dark-colored and heavy, with a foliated or schistose (flaky) structure. The small flakes of black and whites. Hornblende alters easily to chloriteThe term Chlorite can refer to the following meanings: Chlorite is a common clay mineral. Chlorites have a 2:1 sandwich structure (2:1 sandwich layer t etrahedral o ctahedral t etrahedral t-o-t. Unlike other 2:1 clay minerals, a chlorite's interlayer spac and epidoteEpidote a mineral species consisting of basic calcium aluminium and iron orthosilicate, Ca(Al, Fe)(SiO)(OH), crystallizing in the monoclinic system. Well-developed crystals are of frequent occurrence: they are commonly prismatic in habit, the direction of. A variety of hornblende that contains less than 5% of iron oxideThere are a number of iron oxides Iron oxides Iron (II) oxide or ferrous oxide (FeO) The black- coloured powder in particular can cause explosions as it readily ignites. Iron (III) oxide or ferric oxide (FeO) known in its natural state as hematite or haems is gray to white in color and named edenite , from its locality in Edenville, New York. Very dark brown to black hornblendes that contain titanium ordinarily are called basaltic hornblende from the fact that they are usually a constituent of basalt and related rocks.

The word hornblende is derived from the German horn and blende, to blind or dazzle. The term blende was often used to refer to a brilliant non-metallic luster, for example, zincblende, and pitchblende, a lustrous form of uraninite.