Basalt with Jasper Veining

Physical Properties

Hardness: 6-7 (Mohs scale), Color: Dark grey to black matrix with yellow/brown bands, Luster: Waxy to vitreous when wet, Structure: Aphanitic matrix with irregular silica veins, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-3.0

Formation & Geological History

Formed through rapid cooling of basaltic lava followed by secondary mineral deposition (silica-rich fluids) filling cracks or voids during hydrothermal activity, often occurring in volcanic terranes or riverbeds.

Uses & Applications

Used primarily as decorative lawn stones, as specimens for amateur collectors, and occasionally for lapidary work such as cabochons or tumbled stones.

Geological Facts

This specimen appears to be water-worn, likely collected from a river or beach where tumbling action smoothed the surface. The yellow banding is likely Jasper, colored by iron oxides within the silica.

Field Identification & Locations

Identify by its heavy weight (density of basalt) and the hardness of the veins which cannot be scratched by a steel knife. Commonly found in the Pacific Northwest, Great Lakes, or volcanic coastlines.

Identified on: 4/28/2026

Mode: Standard