CHRYSOCOLLA, a hydrous copper silicate occurring as a decomposition product of copper ores. It is never found as crys tals, but always as encrusting and botryoidal masses. It is green or bluish-green in colour, and often has the appearance of opal or enamel, being translucent and having a conchoidal fracture with vitreous lustre ; sometimes it is earthy in texture. Not being a definite crystallized substance, it varies widely in chemical com position, the copper oxide (CuO) , for example, varying in differ ent analyses from 17 to 67%. The hardness (2-4) and sp. gr. (2.o-2.8) are also variable. The mineral occurs in the upper parts of veins of copper ores, and has resulted from their alteration by the action of waters containing silica in solution. Pseudomorphs of chrysocolla after various copper minerals (e.g., cuprite) are not uncommon. It is found in most copper mines. The name chryso colla (from xpvcTos, gold and K6XXa, glue) was applied by Theo phrastus and other ancient writers to materials used in soldering gold, one of which, from the island of Cyprus, may have been identical with the mineral now known by this name. Borax, which is used for this purpose, has also been called chrysocolla.