The most common amphibole mineral, forming dark prismatic crystals with a characteristic 56°/124° cleavage angle. Color: Dark green to black. Luster: Vitreous to dull. Streak: White to gray. Cleavage: Good in two directions at 56° and 124°. Hardness: 5-6. Transparency: Translucent to opaque. Crystal system: Monoclinic. Chemical formula: Ca₂ Mg,Fe,Al ₅ Al,Si ₈O₂₂ OH ₂. Specific gravity: 3.0-3.5. Formation: Crystallizes from intermediate to mafic magmas and forms during medium-grade metamorphism. Common geological settings: Worldwide; essential mineral in diorite, andesite, amphibolite, and hornblende gneiss. Common look-alikes and related entries: Augite, Tourmaline, Arfvedsonite.
These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
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GeoMiner
Last updated
2026-03-30T14:36:45.770811+00:00
Review status
Published; not independently peer-reviewed
IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
The most common amphibole mineral, forming dark prismatic crystals with a characteristic 56°/124° cleavage angle.
How can you identify Hornblende?
Compare several properties rather than relying on colour alone. This entry records colour: Dark green to black; lustre: Vitreous to dull; streak: White to gray; Mohs hardness: 5-6; cleavage: Good in two directions at 56° and 124°; crystal system: Monoclinic; transparency: Translucent to opaque. Confirm an important identification with additional field tests or qualified laboratory work.
How does Hornblende form?
Crystallizes from intermediate to mafic magmas and forms during medium-grade metamorphism.
Where is Hornblende commonly found?
Worldwide; essential mineral in diorite, andesite, amphibolite, and hornblende gneiss.
What is Hornblende commonly confused with?
Hornblende may be confused with Augite, Tourmaline, Arfvedsonite. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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