Hibonite
Hibonite, 1.6 cm (0.63 in) sharp and lustrous crystal from Esiva eluvials, Maromby Commune, Amboasary District, Anosy (Fort Dauphin) Region, Tuléar (Toliara) Province, Madagascar
General
CategoryOxide minerals
Formula
(repeating unit)		(Ca,Ce)(Al,Ti,Mg)12O19
IMA symbolHbn[1]
Strunz classification4.CC.45
Crystal systemHexagonal
Crystal class
  • Dihexagonal dipyramidal (6/mmm)
  • H-M symbol: (6/m 2/m 2/m)
Space groupP63/mmc
Unit cella = 5.56, c = 21.89 [Å]; Z = 2
Identification
ColorBrownish black to black; reddish brown in thin fragments; blue in meteorite occurrence
Crystal habitPrismatic platy to steep pyramidal crystals
Cleavage{0001} good, {1010} parting
FractureSubconchoidal
Mohs scale hardness7+1⁄2–8
LusterVitreous
Streakreddish brown
DiaphaneitySemitransparent
Specific gravity3.84
Optical propertiesUniaxial (-)
Refractive indexnω = 1.807(2), nε = 1.79(1)
PleochroismO = brownish gray; E = gray
References[2][3]

Hibonite is a mineral with the chemical formula (Ca,Ce)(Al,Ti,Mg)12O19, 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, (Fe,Mg)Al12O19)) an alteration mineral from the Allende meteorite.[4] Hibonites were among the first minerals to form as the disk of gas and dust swirling around the young sun cooled.[5]

A very rare gem, hibonite was discovered in 1953 in Madagascar by Paul Hibon, a French prospector.[6]

Colour

Hibonite can vary in colour, from a bright blue, to green, to orange, to a nearly black deep brown. The colour is related to the degree of oxidation; meteoritic hibonite tends to be blue.[7]

See also

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ "Handbook of Mineralogy" (PDF).
  3. ^ "Hibonite: Hibonite mineral information and data". www.mindat.org.
  4. ^ "IMA Mineral List with Database of Mineral Properties". rruff.info.
  5. ^ "A Year in Review and a Look to the Future". Field Museum of Natural History. January 11, 2019. Retrieved 4 December 2021.
  6. ^ "Hibonite gemstone information". www.gemdat.org.
  7. ^ Ihinger, Phillip D.; Stolper, Edward (May 1986). "The color of meteoritic hibonite: an indicator of oxygen fugacity". Earth and Planetary Science Letters. 78 (1): 67–79. Bibcode:1986E&PSL..78...67I. doi:10.1016/0012-821X(86)90173-1.
Wikimedia Commons has media related to Hibonite.


Categories