CAIRNGORM  , a yellow or

brown variety of quartz, named from Cairngorm or Cairngorum; one of the peaks of the Grampian Mountains in Banffshire, Scotland . According to Mr E . H . Cunningham-Craig, the mineral occurs in crystals lining cavities in highly-inclined veins of a fine-grained granite running through the coarser granite of the main mass: Shallow pits were formerly dug in the kaolinized granite for sake of the cairngorm andthe mineral was also 'found as pebbles in the bed of the river Avon . Cairngorm is a favourite ornamental stone in Scotland, being set in the lids of snuff-mulls, in the handles of dirks and in brooches for Highland costume . A rich sherry-yellow colour is much esteemed . Quartz of yellow, and brown colour is often known in trade as " false topaz," or simply " topaz." Such quartz is found at many localities in Brazil, Russia and Spain . Much of the yellow quartz used in jewellery is said to be " burnt amethyst "; that is, it was originally amethystine quartz, the colour of which has been modified by heat (see AMETHYST) . Yellow quartz is sometimes known as citrine;. when the quartz presents a pale brown tint it is called " smoky quartz "; and when the brown is so deep that the stone appears almost black it is termed morion . The brown colour has been referred to. the presence of titanium .