sapphirin

Sapphirin is a rare silicate mineral belonging to the osumilite group. It is characterized by its distinctive blue to greenish-blue color, which gives it its name, reminiscent of sapphire. The chemical formula for sapphirin is (Mg,Al)8(Al,Si)6O20. It typically forms in high-grade metamorphic rocks, particularly those that have undergone granulite facies metamorphism. It is often found in association with other high-temperature minerals such as cordierite, spinel, and hypersthene.

The mineral is known for its vitreous luster and conchoidal fracture. While it can exhibit pleochroism, meaning it appears to have different colors when viewed from different angles, this is usually subtle. Sapphirin is generally opaque to translucent. Its hardness on the Mohs scale is typically between 7 and 8, indicating it is a relatively hard mineral.

Geographically, sapphirin occurrences are limited. Notable locations include the Fiskenæsset complex in Greenland, parts of Sri Lanka, Madagascar, and some occurrences in Finland and Norway. Due to its rarity and the specific geological conditions required for its formation, sapphirin is not commonly encountered by mineral collectors or in commercial applications. It is primarily of interest to mineralogists and geologists studying metamorphic processes and the composition of the Earth's crust.