Pietersite is a rare dark-gray or reddish breccia aggregate (rock made up of fragments embedded in a matrix), comprised mostly of hawk’s eye and tiger’s eye. Pietersite from Namibia was first described in 1962 by Sid Pieters, who named it in his father’s honor. The term “pietersite” is now used as a general term to describe the brecciated tiger’s eye.
Pietersite is characterized by its distinctive swirls or streaks of gold or orange, due to the crocidolite inclusions within a microcrystalline silica host. Crocidolite is the same material responsible for the tiger’s eye chatoyancy. When polished, the inclusions in pietersite exhibit chaotic chatoyancy whereas in the tiger’s eye, the inclusions are arranged in parallel lines and give the appearance of a continuous line. [Source]