FLUORITE WITH CHALCOPYRITE & ARSENOPYRITE

ABOUT THE SPECIMEN Densely grown, partially twinned crystals of highly transparent, pleasant purple fluorite cubes, accented all around to varying degrees by quartz points, arsenopyrite, and chalcopyrite. Much of the chalcopyrite is dotted along the front faces of the fluorite, giving it a glittery look under strong lighting. The fluorite also has a layer of iridescence along the faces, though this was difficult to photograph.   VIDEO   MORE INFO Yaogangxian is one of China's largest tungsten-tin deposits, developed in the contact aureole of a Mesozoic composite pluton - zircon U-Pb dating places the biotite monzogranite at roughly 155 Ma and the associated muscovite granite at 133 Ma - intruded into Cambrian through Jurassic sediments. Fluorite crystallized during the final hydrothermal stage, crosscutting earlier wolframite-quartz and sulfide veins as fluids cooled and fluorine activity peaked; fluid inclusion microthermometry from peer-reviewed work confirms this stage operated at lower temperatures and salinities than the primary tungsten mineralization. Color at Yaogangxian is predominantly attributed to irradiation-induced lattice defects and trace rare earth elements, accounting for the full range from water-clear through sky-blue to deep violet - frequently within a single crystal as concentric phantom zones recording shifting fluid chemistry. Crystals are sharp cubes, occasionally with minor octahedral modification, and the complex internal zoning is the defining characteristic: most prized pieces show a saturated purple or blue core ghosted inside a paler exterior. The mine has produced sporadically but continuously since at least the 1990s, with certain pockets yielding entirely distinct color suites from anything previously seen; supply is ongoing but highly pocket-dependent, making quality deeply inconsistent year to year.