09-10-2023-2038 - draft (Kimberlite pipes, etc., draft)

Mount Hypipamee Crater, Atherton Tableland, Queensland, Australia. This residue of a pipe is about 100 m (330 ft) across.

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 pipes 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. 

https://en.wikipedia.org/wiki/Volcanic_pipe