igneous
Polished pebble, likely basalt or altered volcanic rock
Fine-grained mafic volcanic rock; exact identification requires testing
AI-generated identification · may be incorrectSmall rounded, tumbled specimen with mottled olive-brown and dark-gray coloration, dull to faintly waxy luster, and no visible crystals. Likely hardness about 5–6 Mohs; cleavage absent and specific gravity approximately 2.8–3.1.
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Physical properties
Small rounded, tumbled specimen with mottled olive-brown and dark-gray coloration, dull to faintly waxy luster, and no visible crystals. Likely hardness about 5–6 Mohs; cleavage absent and specific gravity approximately 2.8–3.1.
Formation & geological history
Probably weathered and water-rounded volcanic rock, potentially basalt containing altered iron- and magnesium-rich minerals. Its geological age cannot be determined from the photograph; basalt forms in many ages and settings, especially lava flows and oceanic crust.
Uses & applications
Commonly used as a decorative pebble, craft stone, or inexpensive lapidary material; it has little commercial value unless distinctive mineralization is present.
Geological facts
The olive coloration may reflect chlorite, epidote, or weathered pyroxene, while brown areas may be iron oxides. A streak, magnetism test, hardness test, and close examination of a fresh surface would improve identification.
Field identification & locations
Common in river gravels, beaches, volcanic terrains, and landscaping supplies. Look for a dense, fine-grained texture and possible weak magnetism; avoid assuming it is a gemstone from color alone.
