Tiger eye is a quartz-bearing material, with which the originally existing mineral (krokydolithe) was replaced by quartz. However its fibrillary structure with was taken over. Such formation is defined as a pseudomorph. The original mineral krokydolithe is bluish in the not wheathered condition. With increasing wheathering degree it discolours yellowish. This quartz is traded in yellow color as tiger´s eye, which weigh-ends due to its fibrous structure a beautiful to light light possesses (Chatoyance), in bluish hue as falcon eye. If one burns tiger´s eye, develops a deeply red material, which is called bull eye.
More informations about this material are given from B.Cairncross in his book “minerals of south africa” (1995) . Another source for informations is afrigemtec