igneous
Polished basalt sphere
Basalt; predominantly plagioclase feldspar, pyroxene, and commonly olivine
AI-generated identification · may be incorrectDark gray to black, fine-grained, matte-to-subvitreous luster; typically hardness 5–6 Mohs, specific gravity about 2.8–3.1, and no visible cleavage. The spherical shape and smooth surface indicate human shaping and polishing; surface texture may reflect vesicles or weathering.
Identified More igneous →
Explore Polished basalt sphere in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, fine-grained, matte-to-subvitreous luster; typically hardness 5–6 Mohs, specific gravity about 2.8–3.1, and no visible cleavage. The spherical shape and smooth surface indicate human shaping and polishing; surface texture may reflect vesicles or weathering.
Formation & geological history
Basalt is an extrusive igneous rock formed when mafic lava rapidly cools, commonly in volcanic fields and oceanic crust. Most basalt is geologically young to ancient, ranging from modern eruptions to Precambrian examples; the sphere itself is manufactured.
Uses & applications
Used as a decorative sphere, worry stone, paperweight, and mineral-collecting object; basalt is also widely used as crushed aggregate, paving stone, building stone, and occasionally cast basalt lining.
Geological facts
Its dark color reflects abundant iron- and magnesium-rich minerals. A magnet may show weak attraction if the basalt contains magnetite, but this is not diagnostic.
Field identification & locations
Identify it by its uniform black fine grain, high density, and lack of glassy transparency or metallic streak; a close inspection may reveal tiny feldspar crystals or vesicles. Common sources include India, China, Mexico, Iceland, and volcanic regions worldwide.
