igneous
Black Granite
Phaneritic Mafic Igneous Rock (likely Gabbronorite or Dolerite)
Hardness: 6-7 Mohs; Color: Dark grey to black with white/grey speckling; Luster: Dull (natural) to Vitreous (polished); Structure: Phaneritic (visible crystals); Specific Gravity: 2.7-3.0.
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black with white/grey speckling
- Luster
- Dull (natural) to Vitreous (polished)
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black with white/grey speckling; Luster: Dull (natural) to Vitreous (polished); Structure: Phaneritic (visible crystals); Specific Gravity: 2.7-3.0.
Formation & geological history
Formed by the slow cooling of magnesium and iron-rich magma beneath the Earth's surface. Regionally associated with the Deccan Traps or Precambrian metamorphic belts in Andhra Pradesh, India.
Uses & applications
Extensively used for countertops, floor tiles, monuments, and religious items (such as the background slab shown).
Geological facts
The region of Guntur, Andhra Pradesh (approx. 16.3N, 80.4E) is internationally famous for its 'Black Galaxy' and 'Jet Black' granite varieties, which are among the most sought-after in the world.
Field identification & locations
Identifiable by its crystalline interlocking texture and extreme hardness (cannot be scratched by steel). Commonly found in quarries throughout Southern India.
