Titanite

Titanite (Sphene)
Titanite crystals on amphibole (image width 2 mm)
General
CategoryNesosilicate
Formula
(repeating unit)
CaTiSiO5
IMA symbolTtn[1]
Strunz classification9.AG.15
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H–M symbol)
Space groupP21/a
Unit cella = 7.057 Å, b = 8.707 Å
c = 6.555 Å; β = 113.81°; Z = 4
Identification
ColourReddish brown, brown, gray, black, yellow, green, or red, colourless
Crystal habitFlattened wedge-shaped crystals, also massive
TwinningContact and penetration on {100}, lamellar on {221}
CleavageDistinct on [110], parting on {221}
FractureSub-conchoidal
Mohs scale hardness5–5.5
LusterSub-adamantine tending to slightly resinous
StreakReddish white
DiaphaneityTranslucent to transparent
Specific gravity3.48–3.60
Optical propertiesBiaxial (+); very high relief
Refractive indexnα = 1.843–1.950
nβ = 1.870–2.034
nγ = 1.943–2.110
Birefringenceδ = 0.100–0.160
PleochroismStrong: X = nearly colorless; Y = yellow to green; Z = red to yellow-orange
2V angle17–40° (measured)
Dispersionr > v strong
Other characteristics Radioactive – may be metamict
References[2][3][4][5]
Titanite crystal model

Titanite, or sphene (from Ancient Greek σφηνώ (sphēnṓ) 'wedge'),[5] is a calcium titanium nesosilicate mineral, CaTiSiO5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals including cerium and yttrium; calcium may be partly replaced by thorium.[6]

  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. ^ "Titanite". Handbook of Mineralogy (PDF).
  3. ^ Titanite Mineral Data, WebMineral.com
  4. ^ Titanite, Mindat.org
  5. ^ a b Dana, James Dwight; Ford, William Ebenezer (1915). Dana's Manual of Mineralogy for the Student of Elementary Mineralogy, the Mining Engineer, the Geologist, the Prospector, the Collector, Etc (13 ed.). John Wiley & Sons, Inc. pp. 299–300. Retrieved 2009-07-06.
  6. ^ Deer, W. A.; Howie, R. A.; Zussman, J. (1966). Introduction to the Rock-Forming Minerals. Longman. pp. 17–20. ISBN 0-582-44210-9.