igneous
Basalt Pebble
Mafic Igneous Rock (Basalt)
Hardness: 5-6 (Mohs scale); Color: Dark grey to black; Luster: Dull/Earthy when weathered; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull/Earthy when weathered
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark grey to black; Luster: Dull/Earthy when weathered; 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 at or very near the Earth's surface. This pebble has been water-worn and smoothed by wave or river action.
Uses & applications
Crushed basalt is used in construction for road base, concrete aggregate, and railroad ballast. Polished pebbles are used in landscaping and massage therapy.
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 extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and lack of visible crystals to the naked eye. Commonly found on volcanic beaches and in riverbeds.
