Tinaksite

Tinaksite (K2Na(Ca,Mn2+)2Ti[O|Si7O18(OH)])[2] is a mineral found in northern Russia. Tinaksite can be grayish-white, yellowish, orange, or brown,[1] and it is often found in charoite.[4] Its name is derived from its composition: titanium (Ti), sodium (Na) potassium (K) and silicon (Si). International Mineralogical Association first recognized tinaksite as a mineral in 1965.

Tinaksite
General
CategorySilicate mineral
Formula
(repeating unit)		K2Na(Ca,Mn2+)2Ti[O|Si7O18(OH)]
Strunz classification9.DG.75
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Identification
ColorPink, Pale yellow, Light brown
Crystal habitFibrous, crystalline or Prismatic, crystalline, or Radial, crystalline
CleavagePerfect in one direction, indistinct in one direction
Mohs scale hardness6
LusterVitreous to glassy
StreakWhite
DiaphaneityTransparent to Translucent
Specific gravity2.82
Density2.82
Optical propertiesBiaxial (+)
Refractive indexnα = 1.593 nβ = 1.621 nγ = 1.666
Birefringenceδ = 0.073
References[1][2][3]

References
  1. http://webmineral.com/data/Tinaksite.shtml
  2. http://www.mindat.org/min-3966.html
  3. Mineralienatlas
  4. http://www.galleries.com/minerals/silicate/tinaksit/tinaksit.htm
  • Rozhdestvenskaya, I. V.; Nikishova, L. V.; Lazebnik, Y. D.; Lazebnik, K. A. (1989). "The crystal structure of tokkoite and its relation to the structure of tinaksite" (PDF). Zeitschrift für Kristallographie: 195–204. doi:10.1524/zkri.1989.189.14.195.
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