Fluorite - Indigo (Blueberry)

Blueberry Fluorite is a distinctive variety of fluorite characterized by its deep indigo to violet-blue coloration. This unique hue results from trace elemental impurities and structural anomalies within the crystal lattice, influencing its optical properties. The mineral is composed of calcium fluoride (CaF₂) and belongs to the halide mineral group. It crystallizes in the isometric system, typically forming cubic crystals, though octahedral and more complex isometric forms are also common. This fluorite variety is predominantly found in the Huanggang Mine, located in Hexigten Banner (Keshiketeng Qi), Chifeng City, Inner Mongolia, China.

The region is renowned for its diverse mineral resources, and the Huanggang Mine has become notable for producing high-quality fluorite specimens, including the distinctive deep blue to violet hues characteristic of Blueberry Fluorite. Unlike most fluorite specimens that fluoresce blue under ultraviolet (UV) light, Blueberry Fluorite exhibits a rare red fluorescence. This unusual red glow is attributed to the presence of trace amounts of rare earth elements, specifically samarium (Sm³⁺) and erbium (Er³⁺), which substitute for calcium in the fluorite crystal structure. These elements act as activators, absorbing UV light and re-emitting it as visible red light. The red fluorescence is typically observed under long-wave UV light and is a distinguishing feature of Blueberry Fluorite specimens from the Huanggang Mine