igneous
Basalt (River Stone)
Afanitic Basalt (primarily Plagioclase Feldspar and Pyroxene)
Hardness: 6.0; Color: Dark grey to charcoal; Luster: Dull/Matte; Crystal structure: Afanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to charcoal
- Luster
- Dull/Matte
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to charcoal; Luster: Dull/Matte; Crystal structure: Afanitic (fine-grained); Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. This specific specimen has been smoothed by fluvial (river) erosion over a long period.
Uses & applications
Used in construction as crushed stone or aggregate, for hot stone massage therapy, and often used as decorative landscaping stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and also makes up most of the ocean floors. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture. Found globally in volcanic regions and riverbeds. Look for smooth, rounded edges if found in water sources.
