igneous
Basalt Pebble (Beach Stone)
Aphanitic Mafic Igneous Rock
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull, earthy to sub-metallic; Texture: Fine-grained (aphanitic), smooth due to water abrasion; Specific Gravity: 2.8 - 3.0
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black
- Luster
- Dull, earthy to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull, earthy to sub-metallic; Texture: Fine-grained (aphanitic), smooth due to water abrasion; Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from rapid cooling of magnesium-rich and iron-rich lava erupted at or very near Earth's surface, subsequently rounded and smoothed by water erosion in a stream, river, or ocean shoreline.
Uses & applications
Commonly collected as smooth beach stones, used in landscaping, aquariums, decorative stone arrangements, and hot stone massage therapy.
Geological facts
Basalt is the most common rock type in the Earth's crust, forming almost all of the oceanic crust. Pebbles like this have undergone thousands of years of natural polishing by ocean waves or river currents.
Field identification & locations
Identified by its uniform dark grey-to-black color, fine-grained smooth texture, and rounded water-worn shape. Commonly found along rocky coastlines, riverbeds, and glacial deposits worldwide.
