Hornblende

(Na,K)_0-1Ca₂(Mg,Fe²⁺,Fe³⁺,Al)₅Si_6-7.5Al_2-0.5O₂₂(OH)₂

Hornblende is a chain silicate in the amphibole group. Hornblende is generally black or dark green with distinctive 60° and 120° crystal faces. Hornblende is found usually in igneous and metamorphic rocks.