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Crystals of geikielite from the Maxwell quarry, Chelsea, Outaouais, Québec, Canada
Category Oxide mineral
(repeating unit)
Strunz classification 04.CB.05
Crystal symmetry Trigonal rhombohedral
H-M symbol: (3)
Space group: R3
Unit cell a = 5.05478(26) Å, c = 13.8992(7) Å; Z=6
Color Black, ruby red uncommon; red internal reflections
Crystal habit Tabular prismatic crystals, also as finely granular masses
Crystal system Trigonal
Cleavage Good on {1011}
Mohs scale hardness 5 - 6
Luster Sub-metallic
Streak Purplish brown
Diaphaneity Opaque to translucent
Specific gravity 3.79 - 4.2
Optical properties Uniaxial (-)
Refractive index nω = 2.310 - 2.350 nε = 1.950 - 1.980
Birefringence δ = 0.360 - 0.370
Pleochroism Weak, O = pinkish red, E = brownish to purplish red
References [1][2][3]

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. Bibcode:1892Natur..46..620F. doi:10.1038/046620b0. 

Further readings[edit]

  • Ghiorso, Mark S. (1990). "Thermodynamic properties of hematite — Ilmenite — Geikielite solid solutions". Contributions to Mineralogy and Petrology 104 (6): 645. 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). 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. 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. 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. 
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