Main Page | See live article | Alphabetical index Hewn kimberlite core sample from the James Bay Lowlands region of Northern Ontario, Canada. Green olivine grains and purplish red garnet are visible. The sample is 13 cm (5 inches) long. Kimberlite is a mica peridotite which occurs at Kimberley, 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 reservoirs. See also: List of minerals This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.