Challacolloite

Challacolloite, KPb2Cl5, is a rare halide mineral. It crystallizes in the monoclinic system (with space group P21/c[2]) and occurs as white fumarolic encrustations on lava. It occurs as intergrowths with cotunnite.[3]

Challacolloite
Honey yellow Challacolloite crystals from the famous locality of La Fossa Crater (Vulcano Island, Aeolian Islands, Sicily, Italy)
General
CategoryMineral
Formula
(repeating unit)
KPb2Cl5
IMA symbolChc[1]
Strunz classification3.AA.55 (10th)
Dana classification11.4.2.1
Crystal systemMonoclinic
Crystal class2/m - Prismatic
Unit cell878.2 ų
Identification
Formula mass630.83 gm
ColourColourless to white
Crystal habitAggregate
FractureBrittle, subconchoidal fragments
Mohs scale hardness2-3
LusterAdamantine/Greasy
StreakWhite
Specific gravity4.77 (Calculated)
Density4.77 g/cm3 (Calculated)
Optical propertiesBiaxial (+), a=2.004, b=2.01, g=2.024, bire=0.0200
Refractive indexnα = 2.004 nβ = 2.010 nγ = 2.024
2V angle67° (calculated)

It was first described from a finding at the Challacollo Mine, Iquique, Chile and thereafter identified in specimens from the 1855 Mount Vesuvius eruption and from the Kudryavyi volcano in the Kuriles and also from the Satsuma-Iwojima volcano in Japan.[4] It was recognized as a valid mineral species by the IMA (International Mineralogical Association) in 2005.[4]

Artificially grown KPb2Cl5 crystals are used for lasers.[5]

  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. Mitolo, D.; Pinto, D.; Garavelli, A.; Bindi, L.; Vurro, F. (May 2009). "The role of the minor substitutions in the crystal structure of natural challacolloite, KPb2Cl5, and hephaistosite, TlPb2Cl5, from Vulcano (Aeolian Archipelago, Italy)". Mineralogy and Petrology. 96 (1–2): 121–128. Bibcode:2009MinPe..96..121M. doi:10.1007/s00710-008-0041-2. S2CID 128797167.
  3. Webmineral
  4. Mindat with location data
  5. Jochen Schlüter, Dieter Pohl and Sergey Britvin; The new mineral challacolloite, KPb2Cl5, the natural occurrence of a technically known laser material, N. Jb. Miner. Abh., 2005, Vol.182/1, p. 95–101 pdf


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