CHRYSOPRASE is a transparent variety of crypto-crystal line silica of an apple-green colour (Gr. Xpvvos, gold and zrpacrov, leek), the latter being due to the presence of nickel, probably in the form of hydrous silicate. A very similar artificial gem may be prepared by immersing chalcedony, in solutions of nickel salts. On exposing a natural chrysoprase to light or heat its colour be comes paler, though this may be restored by placing the stone in a damp medium. It is surprising that the colour of the natural gem should be susceptible to the action of light and heat, whilst the artificial product is quite unaffected. (Precious Stones, by Max Bauer; trans. L. J. Spencer, 1904.)