kornerupine

Kornerupine is a rare borosilicate mineral that contains aluminum and magnesium or iron in its crystal structure. It belongs to the borosilicate silicate group, with its composition reflecting the incorporation of boron, silicon-oxygen tetrahedra, and variable amounts of Mg or Fe and Al. In mineralogical practice, two endmember forms are recognized: kornerupine-(Mg) and kornerupine-(Fe), corresponding to the predominant Mg or Fe content.

In hand specimen, kornerupine typically forms as prismatic, elongated crystals or as granular aggregates. It has a glassy to sub-vitreous luster and a color range that is generally greenish to brown. The mineral is usually translucent to transparent and has a relatively medium hardness for silicates, around the mid-range on the Mohs scale. Its cleavage is rarely prominent, and its fracture is uneven.

Kornerupine occurs in high-temperature metamorphic environments and is also reported from some pegmatites. It has been found in various localities around the world, often in rocks where aluminous minerals and boron-bearing phases are present. The mineral can occur in association with other metamorphic borosilicates and aluminous silicates, reflecting its origin in metamorphic differentiation and metasomatic processes.

The name kornerupine honors a Danish mineralogist associated with the study of this mineral. Because of its rarity, kornerupine has limited industrial use and is primarily of interest to mineral collectors and researchers studying borosilicate and metamorphic mineral systems.