igneous
Polished black-and-white stone, likely gabbro or diorite
Gabbro/diorite; chiefly plagioclase feldspar, pyroxene, and possibly amphibole or biotite
AI-generated identification · may be incorrectDark greenish-black, polished, medium- to coarse-grained with irregular pale mineral patches; likely Mohs 6–7, vitreous to dull luster, no obvious cleavage on the rounded surface, and specific gravity about 2.8–3.1.
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Physical properties
Dark greenish-black, polished, medium- to coarse-grained with irregular pale mineral patches; likely Mohs 6–7, vitreous to dull luster, no obvious cleavage on the rounded surface, and specific gravity about 2.8–3.1.
Formation & geological history
A slowly cooled intrusive igneous rock formed when magma crystallized deep within Earth, generally during Precambrian to younger continental crust formation; the specimen has been tumbled or polished.
Uses & applications
Used as decorative stone, countertops, architectural aggregate, landscaping material, and an inexpensive lapidary or worry stone.
Geological facts
Gabbro is the coarse-grained intrusive equivalent of basalt; diorite is compositionally intermediate and commonly has contrasting black-and-white “salt-and-pepper” coloration.
Field identification & locations
Identify it by its dense black-and-white crystalline texture, lack of layering, and inability to scratch it with a steel knife easily; common sources include India, Brazil, Scandinavia, and North America. Exact identification requires a fresh surface or thin-section analysis.
