Unique specimen of cactus quartz, also called spirit quartz, from South Africa.

How is cactus quartz formed?

The physical conditions include an unusual, secondary crystallizing event (one for the crystal, another for the spiky cactus formation). In the case of cactus quartz, the conditions coincided in some of the oldest rocks found on earth, dated 2.3 billion years, in South Africa. Two separate crystallizing phases occurred, probably triggered by distinct geological happenings, such as volcanic activity, and subsequent cooling phases.