The kimberlite is an olivine - and phlogopithaltiges, blue-green to black ultramafic rocks of magmatic origin, which is expected to the group of peridotites and accessorial can lead diamonds. Other ingredients include orthopyroxene, clinopyroxene, rutile, perovskite and garnet pyropreicher. The composition of kimberlite corresponds to the origin of its territory, the upper mantle. The density is 3.3 to 5.7 g / cm ³.
The kimberlite was named after the South African city of Kimberley. The first scientific description and name embossing of the rock comes from Henry Carvill Lewis and was published in 1887. The sample material to come from the Dutoit's Pan mine in Kimberley.
Formation and degradation
The rock is conveyed through the pipes, so-called the surface. This is very profound, vertical vents of volcanic origin. For this reason kimberlites occur at the surface almost completely as volcanic debris rocks ( breccias ) on. Is found only in the root zones of kimberlite pipes as solidified gangue. Depending on the specific training massive kimberlites (mostly warehouse aisles and aisles ), intrusive kimberlite breccia and kimberlite tuffs are distinguished. Next to diamonds It also includes fragments of other foreign rocks ( xenoliths ), who were torn from the eruptions from the deep earth's crust in the air, especially eclogite. Where the kimberlites have entered under more peaceful conditions in columns and corridors, find the way, no diamonds. The first bluish- green rock ( Blue Ground ) takes under the influence of weathering on the Earth's surface a yellowish- brown color to (Yellow Ground ).
The result, most of today Kimberlite before 70 to 150 million years ago, the oldest kimberlite are, however, already about 1.2 billion years ago. They are found in Africa, Australia, North America, India, Brazil and Siberia. In general, the occurrence of kimberlites is bound to kratonische continental blocks.
If there is enough content kimberlite pipes may represent primary deposits of diamonds. The rearranged by water diamonds Weathered the leading diamond kimberlite, you can (eg, soap deposits in streams, rivers and coastal areas ) form secondary deposits.
The first kimberlite was found in South Africa. Later, it was also in Siberia leading diamond kimberlites, Sierra Leone followed in 1961.