Kimberlite pipe

Kimberlite pipes

In kimberlite pipes, the eruption ejects a column of overlying material directly over the magma column, and does not form a large above-ground elevation as typical volcanoes do; instead, a low ring of ejecta known as a tuff ring forms around a bowl-shaped depression over the subterranean column of magma. Over time, the tuff ring may erode back into the bowl, leveling out the depression by filling it with washed-back ejecta. Kimberlite magmas have extremely high xenolith and xenocryst content (>30%). Kimberlite xenoliths are the source of most of the world's commercial diamond production, and also contain other precious gemstones and semi-precious stones, such as garnets, spinels, and peridot.