Rock Identifier
Basalt Pebble with Epidote/Olivine (Vitreous Basalt (SiO2 with Ca/Mg/Fe silicates)) — igneous
igneous

Basalt Pebble with Epidote/Olivine

Vitreous Basalt (SiO2 with Ca/Mg/Fe silicates)

Hardness: 6-7 Mohs; Color: Dark grey to black with green/yellow inclusions; Luster: Dull/Matte (pebble) to Vitreous (crystalline parts); Structure: Fine-grained/Aphanitic; Specific Gravity: 2.8–3.0

Hardness
6-7 Mohs
Color
Dark grey to black with green/yellow inclusions
Luster
Dull/Matte (pebble) to Vitreous (crystalline parts)
Identified More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Dark grey to black with green/yellow inclusions; Luster: Dull/Matte (pebble) to Vitreous (crystalline parts); Structure: Fine-grained/Aphanitic; Specific Gravity: 2.8–3.0

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the Earth surface. This specific specimen has been rounded by fluvial (river) or glacial transport processes which smoothed its edges.

Uses & applications

Common basalt is used in construction aggregate, road base, and railroad ballast. Small water-worn pebbles are popular for decorative landscaping, 'worry stones,' and aquarium substrate.

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 extensively on the Moon and Mars.

Field identification & locations

Identify in the field by its dark weight and fine grain; it will not scratch with a copper penny but can be scratched by a steel file. Commonly found in volcanic regions, riverbeds, and glacial till. This specimen shows 'weathering rinds' where minerals are oxidizing.

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