I've heard from a stalker that Ben a Bhuird is a popular place for hunting them (cairngorm stones). I found some long thin crystals of dark smokey cairngorm stone up near Corrie Sputan Dearg of Ben MacDuibh. There are rumours of gold in various burns in the highlands, though I believe it is in such low quantities that it is not profitable to search seriously for it. In Victorian times there was quite an industry in the cairngorms, finding the smokey quartz which was very trendy then. I heard that a man found a crystal weighing sixty pounds, and presented it to Queen Victoria, who granted him sixty pounds sterling in return, surely a magnificent sum in those days! Happy hunting!