igneous
Basalt (River Pebble)
Basalt
Hardness: 6-7 on Mohs scale. Color: Dark grey to black. Luster: Dull or earthy when unpolished. Crystal structure: Aphanitic (fine-grained), often composed of pyroxene, plagioclase feldspar, and olivine.
- Hardness
- 6-7 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull or earthy when unpolished
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on Mohs scale. Color: Dark grey to black. Luster: Dull or earthy when unpolished. Crystal structure: Aphanitic (fine-grained), often composed of pyroxene, plagioclase feldspar, and olivine.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specific specimen has been rounded by fluvial (river) or coastal erosion during the Holocene era.
Uses & applications
Used extensively in construction as aggregate, in road base, and concrete. In polished form, it is used for massage stones, landscaping, and decorative aquariums.
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 in abundance on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (high density), dark color, and fine-grained texture. To find these, look in dried riverbeds or rocky beaches. Watch for a lack of visible large crystals compared to granite.
