igneous
Basalt with Magnetite inclusions
Basalt (Mafic silicate rock) potentially containing Magnetite (Fe3O4)
Hardness: 6 (Mohs scale); Color: Dark grey to black with metallic silver flecks; Luster: Sub-metallic to dull; Structure: Fine-grained (aphanitic); Specific Gravity: 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black with metallic silver flecks
- Luster
- Sub-metallic to dull
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black with metallic silver flecks; Luster: Sub-metallic to dull; Structure: Fine-grained (aphanitic); Specific Gravity: 3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the surface of a terrestrial planet or the moon. Most specimens date from the Cenozoic era or are found in active volcanic zones.
Uses & applications
Used primarily in construction (crushed stone, concrete aggregate) and road base. Magnetite-rich varieties are studied for paleomagnetism and industrial iron extraction.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up most of the ocean floor. When it contains significant magnetite, it can actually deflect a compass needle.
Field identification & locations
Identify in the field by its dark color, heavy weight (density), and fine-grained texture. Use a strong magnet to see if it exhibits magnetic attraction, common in dark volcanic specimens. Found globally in volcanic regions like Iceland, Hawaii, and the Pacific Northwest.
