igneous
Basalt Pebble
Extrusive Aphanitic Basalt
Hardness: 6 (Mohs scale), Color: Dark grey to black or reddish-brown (when weathered), Luster: Dull to sub-vitreous, Crystal Structure: Microcrystalline (aphanitic), Specific Gravity: 2.8–3.0, Cleavage: None
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black or reddish-brown (when weathered), Luster: Dull to sub-vitreous, Crystal Structure: Microcrystalline (aphanitic), Specific Gravity: 2.8–3.0, Cleavage: None
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or moon. This specific pebble shows signs of river or beach erosion (rounding).
Uses & applications
Commonly used as crushed stone for construction, road base, railroad ballast, and high-quality basalt fiber. Polished pebbles are used for landscaping and stone 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 on the Moon and Mars in the form of 'Maria' (dark plains).
Field identification & locations
Identify in the field by its dark color, heavy weight (density), and fine-grained texture. It will not scratch easily with a steel knife. Commonly found on volcanic islands and coastal areas.
