Basalt with Magnetite

Physical Properties

Hardness: 6-6.5 (Mohs); Color: Dark grey to black; Luster: Dull to sub-metallic with sparkly micro-crystals; Structure: Aphanitic/Fine-grained; Density: High specific gravity due to iron content.

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. This specimen specifically appears to be a water-worn beach pebble, likely from a volcanic coastline.

Uses & Applications

Basalt is used extensively in construction for aggregate, road base, and railroad ballast. This specific small pebble has minimal industrial use but acts as a fine example for amateur geology collections.

Geological Facts

Basalt is the most common rock in the Earth's crust and makes up most of the ocean floor. When it contains high amounts of magnetite, small fragments can be attracted to a strong magnet.

Field Identification & Locations

Identify by its weight (heavier than expected for its size), dark color, and fine-grained texture. Often found on volcanic beaches or near ancient lava flows. Test with a magnet to confirm the presence of magnetite grains.

Identified on: 4/26/2026

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