Kimberlites are a kind of volatile-rich potassic ultrabasic rocks. Usually, they exhibit a distinctive inequigranular texture resulting from the presence of macrocrysts set in a fine grained matrix. The megacryst/macrocryst collection consists of rounded anhedral crystals of magnesian ilmenite, Cr-poor titanian pyrope, olivine, Cr-poor clinopyroxene, phlogopite, enstatite and Ti-poor chromite. Olivine is the dominant member of the macrocryst assemblage. The matrix minerals may comprise: second generation euhedral primary olivine and/or phlogopite, together with perovskite, spinel (titaniferous magnesian aluminous chromite, titanian chromite, members of the magnesian ulvospinel-ulvospinel-magnetite series), diopside (Al- and Ti- poor), monticellite, apatite, calcite, and primary late-stage serpentine (commonly Fe rich). A few kimberlites contain late-stage poikilitic eastonite phlogopites. Nickeliferous sulphides and rutile are familiar accessory minerals. The substitute of early-formed olivine, phlogopite, monticellite, and apatite by deuteric serpentine and calcite is common. Evolved members of the clan may be devoid of, or poor in, macrocrysts, and composed fundamentally of calcite, serpentine, and magnetite together with minor phlogopite, apatite and perovskite.

Diamonds are generally formed when extreme heat (temperatures of 2200 degrees Fahrenheit) and extreme pressure cause carbon atoms to crystallize forming diamonds approximately ninety miles under the earth's surface. Diamonds reach the surface of the earth through volcanic pipes, or channels or via placer, alluvial deposits. The diamond is the hardest of all known bodies securing a level of 10 (harder than steel) on the Mohs Hardness Scale.
Natural diamonds are usually found in the following environments:
* Volcanic pipes or channels generally referred to as kimberlites. A kimberlite is the blue rock characteristic of these volcanic pipes. At last when a volcano erupts diamonds are also deposited on, or near, the surface.
* Placer Deposits - Certain kimberlite host rock is washed away by streams and rivers and the diamonds are deposited in the stream sands in 'placer deposits'
The widespread forms of diamonds are the regular octahedron and the rhombic dodecahedron; the former bounded by eight equilateral triangles, and the latter by twelve rhomb's, or lozenge-shaped surfaces. The faces of the crystals are usually more or less curved, or convex, whilst those of other crystalline bodies, with few exceptions, are flat. Not uncommonly the Diamond takes the form of a six-faced octahedron, which, by the rounding of its eight-and-forty faces becomes almost spherical or approaches a small ball in shape. In certain cases the crystals are curiously "twinned ".

The external surface of a crystal of Diamond is generally smooth; but at times it is indented with triangular impressions, and in certain cases has lines parallel to the edges of the octahedral faces. Some Diamonds possess a rough surface, resembling poorly polished glass, and are often dull, as though covered with a thin coating of gum. These are generally cut into very fine white stones.

Diamonds come up to the Earth's surface in rare molten rock, or magma that originates at great depths. Carrying diamonds and other samples from Earth's mantle, this magma rises and erupts in small but fierce volcanoes. Just underneath such volcanoes is a carrot-shaped "pipe" filled with volcanic rock, mantle fragments, and some embedded diamonds. The rock is termed as kimberlite after the city of Kimberley, South Africa, where the pipes were first discovered in the 1870s. Another rock that yields diamonds is lamproite.

Kimberlite usually occurs in the Earth's crust in vertical structures which are called as kimberlite pipes. They are the most important source of mined diamonds.

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