igneous
Basalt River Pebble
Mafic volcanic rock (Basalt)
Hardness: 6.0; Color: Dark grey to charcoal; Luster: Dull/Sub-metallic; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0.
- Hardness
- 6
- Color
- Dark grey to charcoal
- Luster
- Dull/Sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to charcoal; Luster: Dull/Sub-metallic; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0.
Formation & geological history
Formed through the rapid cooling of low-viscosity lava rich in magnesium and iron. This specific specimen has been rounded and smoothed by mechanical erosion in a high-energy aquatic environment, such as a river or coastal beach.
Uses & applications
Used primarily in decorative landscaping, aquarium decor, and high-quality specimens are used in 'hot stone' therapeutic massage. On a larger scale, basalt is used in road base and concrete aggregate.
Geological facts
Basalt is the most common rock type on Earth's surface, making up the majority of the ocean floor and much of the rocky planets in our solar system, including Mars and Venus.
Field identification & locations
Identify by its dark color, heavy weight for its size, and the lack of visible crystal grains to the naked eye. Often found in volcanic regions or in alluvial deposits downstream from volcanic highlands.
