Habit: Green, dark green to brownish green to black. Prismatic crystals, but more commonly bladed and unterminated. Vitreous to pearly luster; semitransparent. White streak.
Environment: Occurs widely in metamorphic rocks, especially in amphibolites, hornblende schists, gneisses and mafic igneous rocks.
Etymology: From Old German words meaning "horn" and "blind" or "to deceive," alluding to the fact that it occurs in ore deposits but does not yield any metal.
Chemical analysis is necessary to distinguish between hornblendes. The two end members of this group are ferrohornblende, which contains iron, and magnesiohornblende, which contains magnesium.