igneous
Kimberlite
Kimberlite (Group I or II)
Hardness: 6-7 (matrix); Color: Dark bluish-gray to greenish-black (serpentinized); Luster: Dull to greasy; Structure: Porphyritic, containing phenocrysts of olivine, phlogopite, and pyrope garnet; Specific Gravity: 2.7–3.3
- Hardness
- 6-7 (matrix)
- Color
- Dark bluish-gray to greenish-black (serpentinized)
- Luster
- Dull to greasy
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Physical properties
Hardness: 6-7 (matrix); Color: Dark bluish-gray to greenish-black (serpentinized); Luster: Dull to greasy; Structure: Porphyritic, containing phenocrysts of olivine, phlogopite, and pyrope garnet; Specific Gravity: 2.7–3.3
Formation & geological history
Formed at extreme depths (greater than 150km) in the Earth's mantle and brought to the surface through deep-seated volcanic eruptions called kimberlite pipes. These eruptions are rare and incredibly fast-moving.
Uses & applications
The primary source of industrial and gemstone diamonds. Also studied by geologists to understand mantle composition and ancient plate tectonics.
Geological facts
Named after the town of Kimberley, South Africa, where a massive diamond rush occurred in the 1870s. Only about 1 in 200 kimberlite pipes contain economic concentrations of diamonds.
Field identification & locations
Identified by its distinctive 'blue ground' or 'yellow ground' (weathered) appearance and the presence of 'indicator minerals' like chrome diopside and pyrope garnet. Found in ancient continental cratons (South Africa, Russia, Canada).
