igneous
Basalt with Calcite Veining
Aphanitic Mafic Igneous Rock (primarily Plagioclase and Pyroxene) with CaCO3 veins
Hardness: 5-6 (base rock); Color: Dark grey to charcoal with white veins; Luster: Dull to sub-vitreous; Structure: Fine-grained/aphanitic; Cleavage: None/Irregular
- Hardness
- 5-6 (base rock)
- Color
- Dark grey to charcoal with white veins
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 5-6 (base rock); Color: Dark grey to charcoal with white veins; Luster: Dull to sub-vitreous; Structure: Fine-grained/aphanitic; Cleavage: None/Irregular
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The white veins formed later through hydrothermal activity where mineral-rich water filled cracks.
Uses & applications
Basalt is used extensively in construction for aggregate, road base, and railroad ballast. This specific small, water-worn pebble is primarily a collection curiosity.
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 in the field by its dark color, heavy weight (high density), and fine grain. The white veins will react (fizz) to dilute hydrochloric acid if they are calcite. Commonly found on beaches or in riverbeds.
