colangite

Colangite is a rare mineral species classified within the aluminosilicate family. It forms in metamorphic and hydrothermal environments and has been reported from several localities worldwide. Crystals are typically prismatic to tabular and may occur as compact aggregates. The mineral commonly exhibits a color range from colorless to pale yellow or green, and it has a vitreous to pearly luster. Mohs hardness is modest, generally around 5 to 6, and the specific gravity is in the low to mid 3 range.

Composition and structure of colangite are variable, but it is described as a complex aluminum- and iron-rich silicate with oxygen and hydrogen in a layered framework. Trace elements such as magnesium, titanium, or manganese may be present. The crystal system is reported as monoclinic or orthorhombic depending on locality, and the structure features layers of silicate sheets with interlayer cations that influence stacking and symmetry.

Occurrence and formation: Colangite occurs in metamorphic rocks—particularly schists and high-grade gneisses—and in hydrothermal veins associated with granitic or other intrusive rocks. It is commonly found together with other aluminosilicates and with iron- and manganese-bearing minerals. The mineral’s stability is affected by temperature, pressure, and the chemical composition of the host rock.

Name and classification: The term colangite is the accepted designation in mineralogical catalogs. The etymology of the name is not widely published, and its precise origin may vary by locality.

Uses and significance: Colangite has no major economic applications. It is of interest to mineral collectors due to its rarity and to researchers studying silicate structures, metamorphic processes, and the petrology of associated rock units.