A fairly chunky piece of rough fluorite from South Africa. This mineral exhibits well formed deep purple coloured crystals on top with a full second layer of green crystals underneath. They can be seen from all sides and the colour is much greener than it appears in our second photo.
Fluorite which is composed of calcium and fluorine is used extensively in industry where it's best known as fluorspar. Some material can have such exceptional optical clarity that it can be used as a lense. The word fluorescence comes from the word fluorite because some crystals have the ability to fluoresce under ultraviolet light.