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Crystals of geikielite from the Maxwell quarry, Chelsea, Outaouais, Québec, Canada
CategoryOxide mineral
(repeating unit)
Strunz classification4.CB.05
Crystal systemTrigonal
Crystal classRhombohedral (3)
(same H-M symbol)
Space groupR3
Unit cella = 5.05478(26) Å
c = 13.8992(7) Å; Z = 6
ColorBlack, ruby red uncommon; red internal reflections
Crystal habitTabular prismatic crystals, also as finely granular masses
CleavageGood on {1011}
Mohs scale hardness5 - 6
StreakPurplish brown
DiaphaneityOpaque to translucent
Specific gravity3.79 - 4.2
Optical propertiesUniaxial (-)
Refractive indexnω = 2.310 - 2.350 nε = 1.950 - 1.980
Birefringenceδ = 0.360 - 0.370
PleochroismWeak, O = pinkish red, E = brownish to purplish red

Geikielite is a magnesium titanium oxide mineral with formula: MgTiO3. It is a member of the ilmenite group. It crystallizes in the trigonal system forming typically opaque, black to reddish black crystals.

It was first described in 1892[4] for an occurrence in the Ceylonese gem bearing gravel placers. It was named for Scottish geologist Sir Archibald Geikie (1835–1924).[3] It occurs in metamorphosed impure magnesian limestones, in serpentinite derived from ultramafic rocks, in kimberlites and carbonatites. Associated minerals include rutile, spinel, clinohumite, perovskite, diopside, serpentine, forsterite, brucite, hydrotalcite, chlorite and calcite.[1]


  1. ^ a b Handbook of Mineralogy
  2. ^ Geikielite on
  3. ^ a b Geikielite on Webmineral
  4. ^ Fletcher, L. (1892). "Geikielite and Baddeleyite, Two New Mineral Species". Nature. 46 (1200): 620–621. Bibcode:1892Natur..46..620F. doi:10.1038/046620b0.

Further reading[edit]

  • Ghiorso, Mark S. (1990). "Thermodynamic properties of hematite — Ilmenite — Geikielite solid solutions". Contributions to Mineralogy and Petrology. 104 (6): 645–667. Bibcode:1990CoMP..104..645G. doi:10.1007/BF01167285.
  • Reynard, B.; Guyot, F. (1994). "High-temperature properties of geikielite (MgTiO3-ilmenite) from high-temperature high-pressure Raman spectroscopy ? Some implications for MgSiO3-ilmenite". Physics and Chemistry of Minerals. 21 (7): 441. Bibcode:1994PCM....21..441R. doi:10.1007/BF00202274.
  • Baura-Peña, M. P.; Martínez-Lope, M. J.; García-Clavel, M. E. (1991). "Synthesis of the mineral geikielite MgTiO3". Journal of Materials Science. 26 (16): 4341. Bibcode:1991JMatS..26.4341B. doi:10.1007/BF00543648.
  • Robie, Richard A.; Haselton, H.T.; Hemingway, Bruce S. (1989). "Heat capacities and entropies at 298.15 K of MgTiO3(geikielite), ZnO (zincite), and ZnCO3 (smithsonite)". The Journal of Chemical Thermodynamics. 21 (7): 743. doi:10.1016/0021-9614(89)90058-X.
  • Gieré, Reto (1987). "Titanian clinohumite and geikielite in marbles from the Bergell contact aureole". Contributions to Mineralogy and Petrology. 96 (4): 496–502. Bibcode:1987CoMP...96..496G. doi:10.1007/BF01166694.
  • Parthasarathy, G. (2007). "Electrical resistivity of nano-crystalline and natural MgTiO3−geikielite at high-pressures up to 8 GPa". Materials Letters. 61 (21): 4329–4331. doi:10.1016/j.matlet.2007.01.097.
  • Mitchell, Jeremy N.; Yu, Ning; Sickafus, Kurt E.; Nastasi, Michael A.; McClellan, Kenneth J. (1998). "Ion irradiation damage in geikielite (MgTiO3)". Philosophical Magazine A. 78 (3): 713. doi:10.1080/01418619808241931.
  • Chao, G. Y.; Hounslow, A. W. (June 1967). "Geikielite; a new Canadian occurrence". The Canadian Mineralogist. 9 (1): 95–100.