Chrysothallite is a rare thallium-bearing chloride mineral with the formula K6Cu6Tl3+Cl17(OH)4•H2O.[3][4] Chrysothallite is unique in being only the second mineral with essential trivalent thallium,[3] a feature shared with natural thallium(III) oxide, avicennite.[5] Another examples of natural thallium chlorides are steropesite, Tl3BiCl6, and lafossaite, TlCl.[6][7] Chrysothallite is one of numerous fumarolic minerals discovered among fumarolic sites of the Tolbachik volcano, Kamchatka, Russia[8] The mineral is named in allusion to its colour and thallium content.[3]

Chrysothallite
General
CategoryHalide mineral
Formula
(repeating unit)
K6Cu6Tl3+Cl17(OH)4•H2O
IMA symbolCry[1]
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
LusterVitreous
StreakWhite
DiaphaneityTransparent
Density2.95 (measured)
Optical propertiesUniaxial (+)
Refractive indexω=1.72, ε=1.73 (approximated)
References[2][3][4]

Notes on chemistry

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Chrysothallite contains a relative high amount of zinc admixture. Zinc is substituting for copper.[3]

Association and origin

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Chrysothallite may be associated with many other minerals:[3]

Crystal structure

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The crystal structure of chrysothallite is unique. Its building elements are:[3]

  • 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

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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

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  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. ^ Mineralienatlas
  3. ^ a b c d e f g 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
  4. ^ a b "Chrysothallite: Chrysothallite mineral information and data". Mindat.org. Retrieved 2016-03-11.
  5. ^ "Avicennite: Avicennite mineral information and data". Mindat.org. Retrieved 2016-03-11.
  6. ^ "Steropesite: Steropesite mineral information and data". Mindat.org. Retrieved 2016-03-11.
  7. ^ "Lafossaite: Lafossaite mineral information and data". Mindat.org. Retrieved 2016-03-11.
  8. ^ "Tolbachik volcano, Kamchatka Oblast', Far-Eastern Region, Russia - Mindat.org". Mindat.org. Retrieved 2016-03-11.