Chalcedony is a species of the flint genus; of which there are two kinds the common chalcedony and the Carnelian. The colour of the former is a nebulous milky grey, in all its shades. It is commonly semitranspa-rent, harder than flint, and brittle. It is found in Ireland, Ferro Isles, Saxony, Silesia, Siberia, Scotland, Cornwall, etc. It is susceptible of a fine polish, is employed as an article of jewellery, and consists of silex, lime, alumina, and a very little iron.