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monocliniccommonSilicates (Amphibole Group)
Hornblende
(Ca,Na)2-3(Mg,Fe,Al)5(Si,Al)8O22(OH)2
Hornblende is a common dark, prismatic rock-forming mineral, often appearing as elongated crystals with characteristic amphibole cleavage.
Hornblende Physical Properties
Mohs Hardness
5Crystal System
monoclinicLuster
vitreousStreak Color
white to gray-greenCleavage
Perfect in two directions at approximately 56° and 124°Fracture
uneven to subconchoidalSpecific Gravity
3.2Colors
dark green, black, brownTransparency
translucent to opaqueType Locality
Worldwide, commonly found in metamorphic and igneous rocks, such as those on Manhattan Island, New York, USA.Mineral Group
Silicates (Amphibole Group)Uses
rock-forming mineral, aggregate, collector specimensAssociated Minerals
quartz, feldspar, mica, garnet, pyroxeneRarity
commonGeological Context
It is a significant constituent of many igneous rocks (e.g., diorite, gabbro, granite) and metamorphic rocks (e.g., amphibolite, hornblende schist, gneiss), forming under a wide range of pressure and temperature conditions.
