English: Kimberlite from the Precambrian of Colorado, USA. (field of view ~6.2 centimeters across)

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.

A decent number of kimberlite bodies have been identified in the Rocky Mountains along the Colorado-Wyoming border. The rock seen here is a kimberlite sample from the diamondiferous Chicken Park Pipe near Red Feather Lakes, Colorado, USA. The Chicken Park Kimberlite Pipe is part of the State Line Kimberlite Field, traditionally considered to represent many kimberlite bodies emplaced at about the same time. Isotopic dating has indicated this is not the case - the Chicken Park Pipe is late Neoproterozoic in age (614 million years).

This sample has deep red garnets and pale green to green serpentine masses (= altered olivine).

Geologic unit: Chicken Park Pipe (Chicken Park Kimberlite), State Line Kimberlite Field, late Neoproterozoic, 614 Ma

Locality: unrecorded/undisclosed site near Red Feather Lakes, northern Larimer County, northern Colorado, USA