hibonite

{{Infobox mineral | name = Hibonite | boxwidth = | boxbgcolor = | image = Hibonite Complete crystal MHNT MIN 2004 0 90 2.jpg | imagesize = | alt = | caption = Hibonite, sharp and lustrous crystal from Esiva eluvials, Maromby Commune, Amboasary District, Anosy (Fort Dauphin) Region, Tuléar (Toliara) Province, Madagascar | category = Oxide minerals | formula = | IMAsymbol = Hbn | molweight = | strunz = 4.CC.45 | dana = | system = Hexagonal | class = | symmetry = P6/mmc | unit cell = a = 5.56, c = 21.89 [Å]; Z = 2 | color = Brownish black to black; reddish brown in thin fragments; blue in meteorite occurrence | colour = | habit = Prismatic platy to steep pyramidal crystals | twinning = | cleavage = {0001} good, {100} parting | fracture = Subconchoidal | tenacity = | mohs = –8 | luster = Vitreous | streak = reddish brown | diaphaneity = Semitransparent | gravity = 3.84 | density = | polish = | opticalprop = Uniaxial (-) | refractive = n = 1.807(2), n = 1.79(1) | birefringence = | pleochroism = O = brownish gray; E = gray | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }}

Hibonite is a mineral with the chemical formula , occurring in various colours, with a hardness of 7.5–8.0 and a hexagonal crystal structure. It is rare, but is found in high-grade metamorphic rocks on Madagascar. Some presolar grains in primitive meteorites consist of hibonite. Hibonite also is a common mineral in the Ca-Al-rich inclusions found in some chondritic meteorites. Hibonite is closely related to hibonite-Fe (IMA 2009-027, ) an alteration mineral from the Allende meteorite. Hibonites were among the first minerals to form as the disk of gas and dust swirling around the young sun cooled.