igneous
Diamond in Kimberlite
Diamond (C in Kimberlite Matrix)
Hardness: 10 (diamond), 6-7 (matrix); Color: Colorless to white (diamond), green-gray to brown (matrix); Luster: Adamantine (diamond), earthy to greasy (matrix); Crystal structure: Isometric (diamond); Specific gravity: 3.5 (diamond), 2.2-3.0 (matrix).
- Hardness
- 10 (diamond), 6-7 (matrix)
- Color
- Colorless to white (diamond), green-gray to brown (matrix)
- Luster
- Adamantine (diamond), earthy to greasy (matrix)
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Physical properties
Hardness: 10 (diamond), 6-7 (matrix); Color: Colorless to white (diamond), green-gray to brown (matrix); Luster: Adamantine (diamond), earthy to greasy (matrix); Crystal structure: Isometric (diamond); Specific gravity: 3.5 (diamond), 2.2-3.0 (matrix).
Formation & geological history
Formed at extreme depths in the Earth's mantle (over 150 km) under high pressure and temperature. Transported to the surface by rapid, explosive volcanic eruptions called kimberlite pipes millions or billions of years ago.
Uses & applications
Primary source for gemstone diamonds used in jewelry; industrial diamonds used for cutting, grinding, and drilling bits; highly valuable for geological research and mineral collecting.
Geological facts
Kimberlite is named after the town of Kimberley in South Africa. Diamonds are the only gemstones made of a single element (Carbon). Most diamonds seen in matrix like this are over 1 billion years old.
Field identification & locations
Identify by a small, greasy-looking glassy octahedron or form embedded in a dark, ultra-mafic brecciated rock. Found almost exclusively in ancient stable continental cratons like those in South Africa, Russia, Canada, and Australia.
