igneous
Polished Black Basalt Pebble
Basalt
Hardness: 6.0; Color: Black to dark gray; Luster: Dull (natural) to Vitreous (polished); Structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6
- Color
- Black to dark gray
- Luster
- Dull (natural) to Vitreous (polished)
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Black to dark gray; Luster: Dull (natural) to Vitreous (polished); 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 at or very near the Earth's surface. These rounded pebbles are often shaped by water erosion in rivers or coastal areas before being mechanically polished.
Uses & applications
Used widely in decorative landscaping, Zen gardens, massage therapy (hot stones), architectural accents, and aquarium substrates.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight for its size, and the lack of visible large crystals. Commonly found on volcanic beaches or in processed landscaping supply stores.
