Cactus Quartz is a distinctive growth type of quartz, most famously from Mpumalanga Province, South Africa. The name comes from its appearance: a central quartz point covered with a “cactus-like” layer of small second-generation crystals.

“Cactus Quartz,” “Fairy Quartz,” “Spirit Quartz,” and “Porcupine Quartz” are all collector/trade names for the same growth habit.

It is not a separate mineral—just a unique epitaxial overgrowth of quartz on quartz.

Cactus quartz forms by secondary silica deposition on an existing quartz crystal. A primary quartz point grows under standard hydrothermal conditions, then the chemistry of the fluid changes—often becoming supersaturated with silica. A second layer of tiny quartz crystals nucleates on the surface of the primary point, these crystals maintain the same structural orientation (epitaxy), giving the spiky “cactus” texture.

Often, iron-rich fluids are present, giving the amethyst coloration or iron-stain coatings.