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Hornblende identification and geology

A common dark-colored amphibole mineral with the generalized formula Ca,Na ₂–₃ Mg,Fe,Al ₅ Al,Si ₈O₂₂ OH ₂, found in a wide variety of igneous and metamorphic rocks. Hornblende is characterized by two cleavage directions intersecting at approximately 56° and 124° the diagnostic amphibole cleavage angle , a vitreous to silky luster, and a Mohs hardness of 5–6. It is one of the most important rock-forming silicate minerals. Field: mineralogy. Example: Hornblende is the dark mineral forming elongated prismatic crystals in diorite and tonalite, easily distinguished from pyroxene by its characteristic 56°/124° cleavage angles.. Related terms: Amphibole, Augite, Cleavage, Inosilicate.

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Sources, scope & corrections

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.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.027557+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Hornblende mean in geology?
A common dark-colored amphibole mineral with the generalized formula Ca,Na ₂–₃ Mg,Fe,Al ₅ Al,Si ₈O₂₂ OH ₂, found in a wide variety of igneous and metamorphic rocks. Hornblende is characterized by two cleavage directions intersecting at approximately 56° and 124° the diagnostic amphibole cleavage angle , a vitreous to silky luster, and a Mohs hardness of 5–6. It is one of the most important rock-forming silicate minerals.
What is an example of Hornblende?
Hornblende is the dark mineral forming elongated prismatic crystals in diorite and tonalite, easily distinguished from pyroxene by its characteristic 56°/124° cleavage angles.
Which earth-science field uses the term Hornblende?
Hornblende is used in mineralogy.
Which terms are related to Hornblende?
Related terms in this reference are Amphibole, Augite, Cleavage, Inosilicate.

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