hornblende: Any of a group ofcommon rock-forming mineralsof the amphibole group withthe generalized formula(Ca,Na)2(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2.Hornblendes consist mainly of calcium,iron, and magnesium silicate.
A dark-colored
rock-forming mineral consisting of silicates
of calcium, iron, and magnesium. It is a
major component of granite and other igneous
and metamorphic rocks.
