igneous
Basalt (Beach Pebble)
Basalt (extrusive volcanic rock)
Hardness: 5-6 (Mohs); Color: Dark grey to black; Luster: Dull to satiny when wetted; Crystal structure: Aphanitic (fine-grained, invisible to naked eye); Specific gravity: 2.8-3.0.
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to black
- Luster
- Dull to satiny when wetted
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to black; Luster: Dull to satiny when wetted; Crystal structure: Aphanitic (fine-grained, invisible to naked eye); 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 specimen has been rounded and smoothed by wave action in a high-energy aquatic environment over thousands of years.
Uses & applications
Used in construction, as road base, concrete aggregate, and decorative landscaping. High-quality smooth stones are used in hot stone massage therapies or as garden accents.
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 in the field by its dark color, heavy weight compared to other beach stones, and lack of visible crystals. Commonly found on beaches near volcanic coastlines or transported by glacial movement.
