Rounded gray-green beach pebble

Fine-grained, matte to weakly dull luster, gray-green color, smoothly water-worn, with no visible crystals or cleavage. Estimated Mohs hardness 5–6 and specific gravity about 2.8–3.1 if basaltic.

Most likely a weathered basaltic pebble formed from rapidly cooled lava, then rounded by river, wave, or glacial transport. Basalt occurs from Precambrian to modern ages, so age cannot be determined visually.

Suitable mainly for collecting, landscaping, crafts, and decorative pebble use; it has little jewelry value unless unusually patterned or polished.

The green tint may reflect chlorite, epidote, or altered iron-bearing minerals. A magnet may show weak attraction if the rock contains magnetite.

Common in volcanic and glacial regions, including the Pacific Northwest, Iceland, Hawaii, Scotland, and parts of the Great Lakes. Confirm with a streak test, hardness test, acid test, and thin-section or laboratory analysis; the image alone cannot distinguish basalt from greenstone, serpentinite, or other dark metamorphic rocks.