igneous
Basalt River Pebble
Basaltic extrusive igneous rock
Hardness: 6-7 (Mohs); Color: Dark grey, black, or greenish-brown when wet; Luster: Dull to vitreous; Crystal structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6-7 (Mohs)
- Color
- Dark grey, black, or greenish-brown when wet
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark grey, black, or greenish-brown when wet; Luster: Dull to vitreous; 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 near the Earth's surface. These specific specimens are water-worn, having been tumbled and smoothed by river or ocean currents over hundreds to thousands of years.
Uses & applications
Used in landscaping, masonry, aquarium decor, and as massage stones (hot stone therapy) due to their heat retention properties.
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 and Mars.
Field identification & locations
Identify by its heavy weight, dark color, and fine texture. Commonly found in riverbeds, volcanic regions, and coastal shorelines. For collectors, look for uniform smoothness and lack of deep pitting.
