File:Kimberlite (Koidu Kimberlite Complex, Jurassic; Yengema-Koidu area, Sierra Leone, West Africa) 2.jpg

English: Kimberlite from the Jurassic of Sierra Leone, Africa. (~6.1 centimeters across at its widest)

Kimberlites and lamproites have significant economic importance because they are host rocks for gem-grade and industrial-grade diamonds. Kimberlites and lamproites are unusual igneous bodies having overall pipe-shaped geometries. Their mode of formation is only moderately understood because they have not been observed forming. They are known from scattered localities throughout the world - only some are significantly diamondiferous. Classic localities for diamonds are India and Brazil. Africa was later discovered to have many kimberlites and is world-famous for producing large numbers of diamonds. Other notable diamondiferous kimberlite-lamproite occurrences include Russia, China, northwestern Australia, and northwestern Canada.

Kimberlites are named for the town of Kimberley, South Africa, where several kimberlite pipes occur. Kimberlites have a gently tapering-downward, pipe-shaped cross-section.

The slightly bluish-green kimberlite sample seen here is from the diamondiferous Koidu Kimberlite Complex of Jurassic age in eastern Sierra Leone, West Africa. The rounded, whitish- to pale green-colored grains are serpentinized olivine crystals having a mesh texture (reticulate texture) (click on the photo once or twice to zoom in). The sample is probably from one of the kimberlite dikes in the area (Dike Zone B, C, or D of Tompkins & Haggerty, 1984).

Location: probably derived from the Yengema-Koidu (Sefadu) area, eastern Sierra Leone, West Africa

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Info. mostly synthesized from:

Linda Tompkins (pers. comm.)

Stuart McRae (pers. comm.)

Tompkins & Haggerty (1984) - Kimberlites I: kimberlites and related rocks. in: Proceedings of the “Third International Kimberlite Conference”, volume 1. Developments in Petrology 11A.