metamorphic
Amphibolite
Amphibolite, composed mainly of hornblende-group amphibole and plagioclase feldspar
AI-generated identification · may be incorrectDark greenish-black with pale mineral flecks and a coarse, interlocking crystalline texture; typically Mohs 5–6, vitreous to dull, with no obvious cleavage in the specimen. Amphibole is commonly monoclinic; specific gravity is about 2.9–3.4.
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Physical properties
Dark greenish-black with pale mineral flecks and a coarse, interlocking crystalline texture; typically Mohs 5–6, vitreous to dull, with no obvious cleavage in the specimen. Amphibole is commonly monoclinic; specific gravity is about 2.9–3.4.
Formation & geological history
Forms when basaltic or gabbroic rocks undergo medium- to high-grade metamorphism, commonly during regional mountain-building. Its age depends on the source rock and metamorphic event.
Uses & applications
Used as dimension stone, aggregate, and sometimes decorative stone; attractive pieces may be polished for display.
Geological facts
The visible light grains are likely plagioclase, while the darker, elongated grains are likely amphibole.
Field identification & locations
Common in metamorphic belts worldwide; identify it by its dark amphibole-rich appearance, pale feldspar flecks, and crystalline texture. The small, rough specimen has limited commercial value.
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