Source: World-wide. Found on virtually every continent in the world.
Chemical: Mostly olivine/pyroxene.
Crystal System: None
Formation: Found is pipes where ancient volcanoes have erupted and been worn down to ground level. South African diamond bearing kimberlite pipes are black. While the blue-ground and yellow-ground kimberlite can be found in other locations. Such as the blue-ground example shown in the photo above from the Crater of Diamonds State Park, Murphreesboro, Arkansas.
Properties: Contains many gemstones in addition to diamonds. These include garnet, rutile, calcite, peridot, and others.
1.39ct rough diamond octahedron on blue-ground kimberlite