Chemistry:Chrysothallite

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Chrysothallite
General
CategoryHalide mineral
Formula
(repeating unit)
K6Cu6Tl3+Cl17(OH)4•H2O
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupI4/mmm
Unit cella = 11.37 Å, b = 26.21 Å (approximated); Z = 4
Identification
ColorGolden-yellow to light yellow
Crystal habittabular
CleavageNone
FractureUneven
TenacityBrittle
|re|er}}Vitreous
StreakWhite
DiaphaneityTransparent
Density2.95 (measured)
Optical propertiesUniaxial (+)
Refractive indexω=1.72, ε=1.73 (approximated)
References[1][2][3]

Chrysothallite is a rare thallium-bearing chloride mineral with the formula K6Cu6Tl3+Cl17(OH)4•H2O.[2][3] Chrysothallite is unique in being only the second mineral with essential trivalent thallium,[2] a feature shared with natural thallium(III) oxide, avicennite.[4] Another examples of natural thallium chlorides are steropesite, Tl3BiCl6, and lafossaite, TlCl.[5][6] Chrysothallite is one of numerous fumarolic minerals discovered among fumarolic sites of the Tolbachik volcano, Kamchatka, Russia[7] The mineral is named in allusion to its colour and thallium content.[2]

Notes on chemistry

Chrysothallite contains a relative high amount of zinc admixture. Zinc is substituting for copper.[2]

Association and origin

Chrysothallite may be associated with many other minerals:[2]

Crystal structure

The crystal structure of chrysothallite is unique. Its building elements are:[2]

  • layer of distorted CuCl4(OH)2 octahedra, in which the octahedra share edges
  • isolated Tl-centered TlCl6 octahedra
  • isolated Tl-centered TlCl4(H2O)2 octahedra
  • KCl6 and KCl9 polyhedra, that connect all the above elements

Origin

Chrysothallite is supposed to be a product of interaction of relatively high-temperature fumarolic minerals with fumarolic gas and atmospheric water, that takes place in temperatures up to 150 °C (302 °F).

References

  1. Mineralienatlas
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Pekov, I.V., Zubkova, N.v., Belakovskiy, D.I., Yapaskurt, V.O., Vigasina, M.F., Lykova, I.S., Sidorov, E.G., and Pushcharovsky, D.Yu., 2015. Chrysothallite K6Cu6Tl3+Cl17(OH)4.H2O, a new mineral species from the Tolbachik volcano, Kamchatka, Russia. Mineralogical Magazine 79(2), 365-376
  3. 3.0 3.1 "Chrysothallite: Chrysothallite mineral information and data". http://www.mindat.org/min-43874.html. Retrieved 2016-03-11. 
  4. "Avicennite: Avicennite mineral information and data". http://www.mindat.org/min-437.html. Retrieved 2016-03-11. 
  5. "Steropesite: Steropesite mineral information and data". http://www.mindat.org/min-38692.html. Retrieved 2016-03-11. 
  6. "Lafossaite: Lafossaite mineral information and data". http://www.mindat.org/min-27521.html. Retrieved 2016-03-11. 
  7. "Tolbachik volcano, Kamchatka Oblast', Far-Eastern Region, Russia - Mindat.org". http://www.mindat.org/loc-5602.html. Retrieved 2016-03-11.