Sklonite

Sklonite is a rare mineral described in mineralogical literature as a hydrated aluminosilicate that forms in high-grade metamorphic rocks. It is generally classified among the silicate minerals and is typically considered to possess monoclinic crystal symmetry. The composition is variable, but sklonite is described as aluminum- and silicon-rich with minor amounts of magnesium and iron, and it may contain trace alkalis and hydroxyl groups.

Physically, sklonite has a Mohs hardness of about 6.0 to 6.5, a color range from colorless to pale yellow, and a white streak. It exhibits a vitreous luster and is translucent to opaque. Cleavage is imperfect, and the fracture is conchoidal to uneven. The measured specific gravity lies approximately between 3.1 and 3.3. Crystals are typically microcrystalline to euhedral and can reach up to a few millimeters in length.

Occurrence and formation sites include high-grade metamorphic terranes where aluminous rocks undergo dehydration and rehydration reactions. Sklonite is most often found in granulite- to amphibolite-facies rocks and is commonly associated with minerals such as garnet, kyanite or sillimanite, and cordierite. It is interpreted as forming under specific pressure–temperature conditions that reflect its stability within aluminous metamorphic systems.

Etymology: the mineral is named after the Sklon region, where it was first identified, in recognition of the locality’s geology.

Uses and significance: due to its rarity, sklonite has no known industrial applications. It is of interest primarily to researchers studying metamorphic processes, phase equilibria in aluminous silicates, and the crystallography of monoclinic minerals. Identification typically relies on X-ray diffraction and electron microprobe analysis.