Jasper, a form of chalcedony and is an opaque rock of virtually any colour stemming from the mineral content of the original sediments or ash. The name means "spotted or speckled stone" and patterns arise during the consolidation process forming flow and depositional patterns in the original silica rich sediment or volcanic ash. Hydrothermal circulation is generally thought to be required in the formation of jasper. The classification and namings of jasper are enormous. Names can derive from the geographical location of where it is found, or location such as rivers and mountains, many are fanciful such as "Forest Fire" or "Rainbow", while others are descriptive such as "Autumn" and "Dalmatian".