Opal

A semi-transparent stone, remarkable for the play of colours that it exhibits. Three varieties are, the oriental opal, called also the noble opal and the harlequin opal, remarkable for its flashes of brilliant colours having a triangular disposition. The affection that the ancients entertained for this beautiful gem was unbounded. The Roman senator Nonnius preferred exile to parting with a brilliant opal the size of a filbert which Marc Antony coveted. The fire opal is furnished principally by Mexico. Its colour, more pronounced than that of the oriental opal, and the carmine or vinous red tint of its fires, permit it to be easily recognized. The common opal displays very little fire; its colour is milk-white, which, joined to a texture extremely homogeneous, renders it semi-transparent. [ L. Dieulafait. ]