metamorphic
Amphibolite
Amphibolite, composed mainly of amphibole and plagioclase feldspar
AI-generated identification · may be incorrectDark gray to black with white feldspar flecks and a coarse, crystalline texture; likely amphibole hardness about 5–6 Mohs, vitreous to dull luster, and no obvious cleavage at this scale. The rock’s exact mineral proportions and specific gravity cannot be confirmed from the image.
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Physical properties
Dark gray to black with white feldspar flecks and a coarse, crystalline texture; likely amphibole hardness about 5–6 Mohs, vitreous to dull luster, and no obvious cleavage at this scale. The rock’s exact mineral proportions and specific gravity cannot be confirmed from the image.
Formation & geological history
Forms when basaltic or other mafic rocks undergo medium- to high-grade regional metamorphism, commonly during mountain building. Its age depends on the source rock and metamorphic event and cannot be determined visually.
Uses & applications
Used as crushed aggregate, dimension stone, and occasionally decorative landscaping stone; attractive pieces may be collected.
Geological facts
Amphibolite is named for amphibole minerals, especially hornblende; its banding or mineral alignment may reflect metamorphic deformation.
Field identification & locations
Look for abundant dark amphibole crystals mixed with lighter plagioclase, often with a coarse or foliated appearance. Found in metamorphic belts worldwide; a small, common hand specimen is typically worth about $2–$15.
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