How do we get our alum blocks?

I had presumed that the alum blocks we use after shaving were mined mineral deposits just carved out of the rock and cut to size, much as common salt (sodium chloride) may be mined; but watching a TV programme on the North Yorkshire coast I now wonder if that is the case.

Is alum mined anywhere in a pure crystalline form, or is it always the product of a longer process which ends in the crystallization of a liqueur?
Suffolk, England
Some are natural, Osma, Taylor & Edwin Jagger are the well know brands that offer natural stones. Some are made from reformed natural off cuts & some are manufactured. There are natural deposits in France (OSMA) & in Pakistan in the Himalayas.