Hibonite
Image: Didier Descouens (CC BY-SA 4.0)
Mineral NameHibonite
Chemical FormulaCa(Al,Ti)12O19
Mohs Hardness7.5
Crystal Systemhexagonal
Streak Colorwhite to pale brown
Cleavagedistinct on {0001}
Fractureuneven to conchoidal
Specific Gravity3.84
Colorsblack, dark brown
Transparencyopaque
Type LocalityEsiva eluvials, Maromby Commune, Amboasary District, Anosy (Fort Dauphin) Region, Tuléar (Toliara) Province, Madagascar
Mineral GroupOxides
Usescollector, scientific research
Associated Mineralsspinel, corundum, perovskite, anorthite
Rarityrare
Description
This image shows a dark, hexagonal prismatic crystal of Hibonite, measuring 1.6 cm. The crystal exhibits a submetallic to dull luster on its striated prism faces, while the basal pinacoids appear rough and uneven.
Geological Context
Hibonite is a rare oxide mineral typically found in highly metamorphosed calc-silicate rocks, marbles, and as a component of calcium-aluminium-rich inclusions (CAIs) in meteorites. It forms under high-temperature, low-pressure metamorphic conditions.
