Geikielite

Geikielite
Crystals of geikielite from the Maxwell quarry, Chelsea, Outaouais, Québec, Canada
General
Category	Oxide mineral
Formula (repeating unit)	MgTiO3
IMA symbol	Gk
Strunz classification	4.CB.05
Crystal system	Trigonal
Crystal class	Rhombohedral (3) (sameH-M symbol)
Space group	R3
Unit cell	a = 5.05478(26) Å c = 13.8992(7) Å; Z = 6
Identification
Color	Black, ruby red uncommon; red internal reflections
Crystal habit	Tabular prismatic crystals, also as finely granular masses
Cleavage	Good on {1011}
Mohs scalehardness	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

Geikieliteis a magnesium titaniumoxide mineralwith formula: MgTiO₃.It is a member of theilmenitegroup. It crystallizes in thetrigonalsystem forming typically opaque, black to reddish black crystals.

It was first described in 1892for an occurrence in the Ceylonese gem bearing gravelplacers.It was named for Scottish geologistSir Archibald Geikie(1835–1924).It occurs inmetamorphosedimpure magnesianlimestones,inserpentinitederived fromultramafic rocks,inkimberlitesandcarbonatites.Associated minerals includerutile,spinel,clinohumite,perovskite,diopside,serpentine,forsterite,brucite,hydrotalcite,chloriteandcalcite.

Further reading

• 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.S2CID98522254.
• 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.S2CID96095190.
• 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.S2CID94170430.
• 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.S2CID86861792.
• 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.Bibcode:1998PMagA..78..713M.doi:10.1080/01418619808241931.
• Chao, G. Y.; Hounslow, A. W. (June 1967)."Geikielite; a new Canadian occurrence".The Canadian Mineralogist.9(1): 95–100.