igneous
Drill Core (Basalt or Andesite)
Volcanic porphyry (mafic to intermediate)
Hardness: 5-7 Mohs; Color: dark grey to black with light crystalline phenocrysts; Luster: dull to earthy; Structure: fine-grained (aphanitic) matrix; Specific Gravity: 2.7-3.0
- Hardness
- 5-7 Mohs
- Color
- dark grey to black with light crystalline phenocrysts
- Luster
- dull to earthy
Identified More igneous →
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Physical properties
Hardness: 5-7 Mohs; Color: dark grey to black with light crystalline phenocrysts; Luster: dull to earthy; Structure: fine-grained (aphanitic) matrix; Specific Gravity: 2.7-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specific specimen is a core sample extracted from deep underground via diamond drilling for mineral exploration.
Uses & applications
Used in geological surveying, mineral exploration, and mining to sample subsurface lithology and identify ore-bearing zones.
Geological facts
The markings on the rock (C-423, Caranundra) indicate it is a sample from a specific drill hole. Drill cores provide the only direct sight into the Earth's crust at great depths.
Field identification & locations
Identify in the field by its cylindrical shape and core-drilling marks. Commonly found near active or historical mining exploration sites in volcanic belts.
