English: (public signage, Laurel Gorge Cultural Heritage Center, between Sandy Hook & Newfoundland, Elliott County, Kentucky, USA)

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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. They 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 that area. Kimberlites have a gently tapering-downward, pipe-shaped cross-section, somewhat like a carrot. Lamproites have a cross-section shape that resembles a martini glass.

Diamondiferous kimberlites are rare and potentially valuable geologic "deposits", so prospectors search for "indicator minerals" that have eroded away and washed downstream. Classic examples are greenish chromian diopside and reddish pyrope garnet.

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See info. at:

en.wikipedia.org/wiki/Kimberlite#Kimberlitic_indicator_mi...