Rahul Sharma (Editor)

Chrysothallite

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Category
  
Halide mineral

Crystal system
  
Tetragonal

Formula (repeating unit)
  
K6Cu6TlCl17(OH)4•H2O

Space group
  
I4/mmm

Crystal class
  
Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m)

Unit cell
  
a = 11.37 Å, b = 26.21 Å (approximated); Z = 4

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

Contents

Association and origin

Chrysothallite may be associated with many other minerals:

  • chlorides: atacamite, avdoninite, belloite, eriochalcite, mitscherlichite, sanguite, carnallite, halite, sylvite;
  • sulfates: antlerite, chlorothionite, kröhnkite, natrochalcite, gypsum, kainite

    • Crystal structure

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

  • 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

    Chrysothallite Wikipedia
    (Text) CC BY-SA