Kimberlite is a
mica peridotite[?] which occurs at
Kimberly, South Africa[?], the source of rich deposits of
diamonds. These diamonds were originally found in decomposed kimberlite which was colored yellow by
limonite, and so was called "yellow ground." Deeper workings encountered less altered rock, undecomposed kimberlite, which miners call "blue ground."
Kimberlite occurs in "kimberlite pipes," vertical columns of rock that rise from deep magma resevoirs.
See also: List of minerals