Unique green fluorite in octahedral form with rock crystal overgrowth

A green fluorite octahedron from Guilin, China, coated with a finely crystalline rock crystal layer. The sugary crystal surface refracts the light in a thousand tiny reflections, while the green fluorite core shimmers through from beneath.

Fluorite crystallizes क्यूबिकly in cubes, octahedra, or combined forms. The green coloration comes from traces of yttrium or rare earths and natural radiation exposure. With a Mohs hardness of 4, fluorite is softer than quartz. It cleaves perfectly along four directions. This property geometrically explains the octahedral shape as octahedral cleavage of the cubic crystal.

The rock crystal overgrowth is the result of a second hydrothermal phase. After the crystallization of fluorite, a more silica-rich solution flowed through the void system. It deposited the sugary quartz crust over the older mineral. Such generational changes are regularly documented in deposits of the Nanling region of South China.

Guilin is known as a premium deposit for stepped fluorite-rock crystal combinations. Mining takes place in deep karst caves, which makes the recovery of large specimens like this difficult and explains their collector's value.

A collector's item that visibly unites two mineral generations and presents mineralogical genesis as a visual layer narrative.