Wiluite

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Wiluite
Wiluite-rh3-48b.jpg
Wiluite crystal from the Wilui River, Siberia
General
Category Sorosilicates
Formula
(repeating unit)
Ca19(Al,Mg,Fe,Ti)13(B,Al,[ ])5Si18O68(O,OH)10
Strunz classification 9.BG.35
Crystal system Tetragonal
Crystal class Ditetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space group P4/nnc
Unit cell a = 15.716, c = 11.704 [Å]; Z = 2
Identification
Color Dark green
Crystal habit Typically as euhedral crystals
Cleavage {100} poor
Fracture Irregular
Mohs scale hardness 6
Luster Vitreous
Specific gravity 3.36
Optical properties Uniaxial (+)
Refractive index nω = 1.721 nε = 1.725
Birefringence δ = 0.004
References [1][2]

Wiluite is a dark green, brownish, or black blocky silicate mineral with formula: Ca19(Al,Mg,Fe,Ti)13(B,Al,[ ])5Si18O68(O,OH)10. It has a Mohs hardness of 6 and a specific gravity of 3.36. It has a vitreous lustre, poor cleavage and an irregular brittle fracture, it crystallizes in the tetragonal system and occurs as well-formed crystals with good external form. It is isostructural with the vesuvianite group and is associated with wollastonite and olive-green grossulars (viluites) in a serpentinized skarn.

The minerals that wiluite and viluite refer to have often been confused, and may refer to grossular,[3][4] or wiluite.[5][6][7] It was discovered in the 1990s and named for the Wilui River region, Sakha Republic (Yakutia), Russia.

Viluite was introduced as a mineral name twice. Von Leonhard used it for a mineral that was considered the same as vesuvianite. However, that material was recently shown to be rich in boron and thus different from vesuvianite; in 1998 that material was named Wiluite. The other author to introduce viluite was Severgin, who used it in reference to what is widely known as grossular, a member of the garnet group.[8]

References[edit]

  1. ^ Webmineral data
  2. ^ Mindat with location data
  3. ^ Viluite Mindat database
  4. ^ Wiluite (of Severgin) Mindat database
  5. ^ Wiluite Mindat database
  6. ^ W - Wiluite World of Gemstones dictionary, accessed online January 25, 2007
  7. ^ V - Viluite World of Gemstones dictionary, accessed online January 25, 2007
  8. ^ de Fourestier, Jeffrey; Glossary of Mineral Synonyms, Canadian Mineralogist Special Publication 2, Mineralogical Association of Canada, Ottawa, Ontario, 1999, 445 pp. ISBN 0921294441

External links[edit]