igneous
Vesicular Basalt with Pyrite
Basalt (MgFe2+)(Si,Al)2O6 containing FeS2 inclusions
Hardness: 5-6 (Basalt) / 6-6.5 (Pyrite); Color: Dark brown to black with metallic gold inclusions; Luster: Dull earthy matrix with metallic crystals; Crystal Structure: Isometric pyrite in fine-grained aphanitic matrix; Specific Gravity: 2.8–3.0.
- Hardness
- 5-6 (Basalt) / 6-6
- Color
- Dark brown to black with metallic gold inclusions
- Luster
- Dull earthy matrix with metallic crystals
Identified More igneous →
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Physical properties
Hardness: 5-6 (Basalt) / 6-6.5 (Pyrite); Color: Dark brown to black with metallic gold inclusions; Luster: Dull earthy matrix with metallic crystals; Crystal Structure: Isometric pyrite in fine-grained aphanitic matrix; Specific Gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The metallic inclusions (likely pyrite) formed through hydrothermal activity within the volcanic rock cavities.
Uses & applications
Primarily used as construction aggregate, road base, and in concrete. Specimens with visible minerals like pyrite are kept as geological collectibles.
Geological facts
Basalt is the most common rock type on Earth's crust and makes up most of the ocean floor. When it contains metallic minerals like pyrite, it demonstrates the chemical diversity of magma and volcanic gases.
Field identification & locations
Identify by its heavy weight, dark color, and fine-grained texture. Pyrite can be identified by its brassy yellow color and 'fool's gold' appearance against the dark background. Commonly found in volcanic fields and oceanic crust outcrops.
