Suanite
Suanite is a rare magnesium borate mineral with the chemical formula Mg2B2O5. It is typically found in high-temperature metamorphic rocks, specifically those that have undergone metamorphism in magnesium-rich, boron-rich environments. This often includes skarns and tactites associated with granitic intrusions.
Suanite typically appears as colorless to pale yellow or greenish, prismatic crystals, often elongated and acicular (needle-like). It can also be found in granular or massive form. The mineral has a vitreous luster and a hardness of 6-6.5 on the Mohs scale. Its specific gravity ranges from 2.89 to 2.95.
Optically, suanite is biaxial positive and exhibits moderate birefringence. Its refractive indices vary depending on the specific light wavelength used for measurement. The mineral is relatively resistant to weathering.
Suanite's formation is dependent on specific geological conditions and the presence of both magnesium and boron. As such, it is not a widespread mineral and is considered quite rare. Known localities include areas in the United States, Russia, and China. It is typically associated with other boron-containing minerals such as ludwigite, szaibelyite, and kotoite, as well as minerals common to metamorphic environments like forsterite, diopside, and spinel.
The name "suanite" is derived from the Chinese name for the Suan-Chwan area in Liaoning Province, China, where the mineral was first discovered and described.