File:Kimberlite (Indian Guide Kimberlite Field, Devonian; Iron Mountain Kimberlite District, NE of Laramie, Wyoming, USA) (14823488105).jpg

Indian Guide Kimberlite from the Devonian of Wyoming, USA (field of view ~4.7 cm across).

Kimberlites and lamproites have tremendous economic importance because they are host rocks for gem-grade and industrial-grade diamonds. Kimberlites & 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. Kimberlites & lamproites are known from scattered localities throughout the world - only some are significantly diamondiferous. Classic localities for diamonds are India and Brazil. Africa was also 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. Several kimberlite pipes occur in the Kimberley area. Kimberlites have a gently tapering-downward, pipe-shaped cross-section. Lamproites have a cross-section more closely resembling that of a martini glass.

The Wyoming Geological Survey has identified several kimberlites and kimberlite fields in Wyoming, including the Indian Guide Kimberlite Field in southeastern Wyoming. Shown above is a sample from an Indian Guide kimberlite dike that consists of serpentinized olivines and garnets having whitish reaction rims. Dike emplacement occurred during the Early Devonian. Kimberlites in this area have intruded through the Sherman Granite, an widespread Proterozoic unit (1.4 billion years) in southeastern Wyoming.