Chiolite
Chiolite is a relatively rare halide mineral with the chemical formula Na5Al3F14. It is a complex fluoride of sodium and aluminum.
Properties:
Chiolite typically occurs as white to colorless, or sometimes yellowish or reddish, crystalline masses. It is transparent to translucent with a vitreous luster. It has a hardness of 4 on the Mohs scale and a specific gravity of approximately 3.0-3.1. The crystal system is monoclinic, though well-formed crystals are rare. Cleavage is distinct in one direction. Chiolite is readily soluble in sulfuric acid.
Occurrence and Formation:
Chiolite is found in association with other fluoride minerals such as cryolite, fluorite, and topaz. It is primarily found in pegmatites and high-temperature hydrothermal deposits. The most notable occurrence is at Ivigtut, Greenland, where it was found alongside cryolite. Other reported occurrences include Russia, the United States (Colorado), and elsewhere.
Uses:
Historically, chiolite, like cryolite, has been used in the electrolytic production of aluminum to lower the melting point of alumina (aluminum oxide). However, due to its rarity compared to cryolite, its industrial importance has been limited. Synthetic cryolite has largely replaced both minerals in this application. Chiolite may also be collected as a mineral specimen by collectors.
Distinguishing Characteristics:
Chiolite can be distinguished from other similar-looking minerals by a combination of its physical properties, including its hardness, specific gravity, cleavage, and association with other fluoride minerals. X-ray diffraction analysis is often used for definitive identification.
Related Minerals:
Cryolite (Na3AlF6) is the most closely related and commonly associated mineral. Other related minerals include fluorite (CaF2), topaz (Al2SiO4(OH,F)2), and other fluoride minerals.