Zunyite

Zunyite is not a rare mineral but is rarely faceted. Crystals are very small and rarely transparent enough for faceting. However, in 1986 relatively large Zunyite crystals (up to 2cm) were found in a prospect pit near Quartzite, Arizona, USA. The chemcal formula of Zunyite is  Al₁₃Si₅O₂₀(OH)₁₆F₂Cl [Aluminum Silicate Hydroxide Fluoride Chloride] and its molecular weight is 1156.74 gm. They were perfect tetrahedra and pale beige-brown in color. Zunyite has a specific gravity of 2.874 (g/cm3) and the refractive index of 1.592 - 1.600 Isotropic. Minute areas of some of these crystals were perfectly transparent, colorless and suitable for faceting gems up to 1/2 carat in size.

Zunyite is found in several localities worldwide but very few produce facet grade crystals. The only location reported to produce such crystals is in the Dome Rock Mountains, near Quartzsite, La Paz County, Arizona, USA.