igneous
Polished gabbro or basalt with quartz/calcite veining
Mafic igneous rock; chiefly plagioclase and pyroxene, with light veins of quartz or calcite
AI-generated identification · may be incorrectDark gray-black, fine- to medium-grained, with a subdued polished luster and pale irregular veins. Estimated hardness is about 5–7, depending on mineral content; cleavage is not obvious and specific gravity is commonly 2.8–3.1.
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Physical properties
Dark gray-black, fine- to medium-grained, with a subdued polished luster and pale irregular veins. Estimated hardness is about 5–7, depending on mineral content; cleavage is not obvious and specific gravity is commonly 2.8–3.1.
Formation & geological history
Formed when mafic magma cooled—slowly underground if gabbro, or rapidly at the surface if basalt—likely during an ancient crystalline-rock episode. The pale veins formed later when mineral-rich fluids filled fractures.
Uses & applications
Used as a decorative stone, jewelry or worry stone, aggregate, and occasionally dimension stone. Its appeal is primarily ornamental rather than high gem value.
Geological facts
The image cannot reliably distinguish gabbro from basalt or identify whether the veins are quartz, calcite, or feldspar without testing. A glassy scratch test and acid test can help separate quartz from calcite.
Field identification & locations
Common in oceanic crust and mafic igneous terrains worldwide, including India, Norway, South Africa, and the western United States. Look for dark interlocking grains, high density, and veins that contrast sharply with the matrix.
