CAIRNGORM, or Cairngorum, a name popularly applied to a wine-yellow or brown variety of rock crystal found, among other localities, on the Grampian Mountains in the south-east of Banffshire, Scotland, the central peak being called Cairngorm. The colour of the crystals, which is due to a minute proportion of iron oxide, varies, passing through those above noted as belonging properly to cairngorms, into a dull grey, smoky quartz, and to a black variety, called morion. The same stone is found in commerce passing under the names of false topaz, Brazilian topaz, occidental topaz, and cinnamon stone (pierre de cannelle of the French). It is found iu many parts of the world, Brazil producing the finest deep brown varieties; but fine stones also come from India, Bohemia, Mexico, and Pennsylvania. It is also found at the Carnbrae Mines, in Cornwall. In the cairngorm district masses weighing as much as 25 lb have been obtained, and an Edinburgh lapidary cut nearly £400 worth of ornamental stones out of a single crystal. The cairngorm is chiefly used for Scotch jewellery, the mounting of gold and silver plaid-brooches, setting in the lids of snuff-mulls, the handles of dirks, <fcc., and the ornamentation of other articles connected with the Highland costume. The stones are most effectively set by covering the undersets entirely with oblong facets arranged in regular rows, surrounding the table with triangular facets and keeping the stone as thick as possible. By this means great brilliancy combined with depth of colour, is secured