The Collaborative International Dictionary of English v.0.48:

cairngorm \cairn"gorm\, Cairngormstone \Cairn*gorm"stone`\
   [Gael. carn a cairn + gorm azure.] (Min.)
   A smoky yellow or brown variety of rock crystal, or
   crystallized quartz, found especially, in the mountain of
   Cairngorm, in Scotland.

   Syn: smoky quartz.
        [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

cairngorm
    n 1: a smoky yellow or brown quartz [syn: cairngorm, smoky
         quartz]