Weathered basalt cobble

Dark gray, rounded, and dull-weathered, with a conspicuous pale tan mineral patch; likely composed mainly of plagioclase and pyroxene, possibly olivine. Basalt is typically Mohs 5–6, with an interlocking fine-grained crystal structure and no prominent cleavage; the photo does not allow the pale patch to be identified reliably.

Basalt forms when iron- and magnesium-rich lava cools at or near the surface; its age and exact origin cannot be determined from the image. The rounded shape suggests transport and abrasion by water or other geological processes.

Commonly used as crushed aggregate, road stone, and construction material; this small cobble is mainly suitable for collecting or display.

The pale spot may be a mineral inclusion or a weathered alteration patch, but a close view or tests would be needed for confirmation.

Look for a dense, dark, fine-grained rock; basalt commonly occurs in volcanic regions and river or beach gravels. The specimen's locality and a fresh broken surface would help confirm identification.