metamorphic
Polished black metamorphic stone, likely serpentinite or amphibolite
Serpentinite (mainly serpentine-group minerals) or amphibolite (hornblende–plagioclase); exact identification requires testing
AI-generated identification · may be incorrectDark gray-black with pale cream veining, waxy to subvitreous luster, and irregular massive texture; typical hardness is about 2.5–5.5 Mohs and specific gravity roughly 2.5–3.3. The polished surface obscures cleavage and crystal size.
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Physical properties
Dark gray-black with pale cream veining, waxy to subvitreous luster, and irregular massive texture; typical hardness is about 2.5–5.5 Mohs and specific gravity roughly 2.5–3.3. The polished surface obscures cleavage and crystal size.
Formation & geological history
Serpentinite forms when ultramafic mantle rocks hydrate during metamorphism; amphibolite forms from basaltic rocks under medium- to high-grade metamorphism. These are generally ancient Precambrian to Phanerozoic rocks formed in tectonic belts.
Uses & applications
Used as ornamental stone, carvings, cabochons, countertops, and collector specimens; serpentinite is also used decoratively in architecture.
Geological facts
The cream patches may be carbonate, quartz, or altered feldspar, while the dark matrix could include serpentine, amphibole, chlorite, or magnetite.
Field identification & locations
Field clues include a dark massive body with pale veins and possible greenish tones; serpentinite is often softer and waxier, whereas amphibolite is harder and denser. Common sources include California, Italy, New Zealand, Canada, and Appalachian metamorphic belts.
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