I offer no apology for including carborundum in my collection. I saw the specimen on a market stall amidst the bric a brac priced at £10, and I could not resist buying it. Carborundum is of course a manufactured mineral made from silicon and carbon. and is also known as silicon carbide. SiC. The method for producing carborundum was patented in 1893 by Edward Goodrich Acherson, and since then it has been one of the most important minerals in many production processes. The life of Acherson is fascinating, and I recommend that the reader should take a close look at his activities. The irridescence is the result of a silicon coating on the mineral surface.