igneous
Basalt River Stone
Basalt
Hardness: 6; Color: Black or dark gray; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8–3.0.
- Hardness
- 6
- Color
- Black or dark gray
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6; Color: Black or dark gray; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava. Likely rounded by fluvial or coastal transport. Consistent with the volcanic geology of Bougainville Island (Papua New Guinea).
Uses & applications
Used in construction as aggregate, for river rock landscaping, and sometimes in hot stone massage or as decorative pocket stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is functionally identical to the lunar mare on the Moon.
Field identification & locations
Identify by its weight (dense for its size), uniform dark color, and fine texture. Common in volcanic island regions like the Solomon Sea area.
