Challacolloite

{{Short description|Chloride mineral}}

{{Infobox mineral

| name = Challacolloite

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| caption = Honey yellow Challacolloite crystals from the famous locality of La Fossa Crater (Vulcano Island, Aeolian Islands, Sicily, Italy)

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| formula = {{chem2|KPb2Cl5}}

| IMAsymbol = Chc{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| molweight = 630.83 gm

| strunz = 3.AA.55 (10th)

| dana = 11.4.2.1

| system = Monoclinic

| class = 2/m - Prismatic

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| unit cell = 878.2 ų

| colour = Colourless to white

| habit = Aggregate

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| fracture = Brittle, subconchoidal fragments

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| mohs = 2-3

| luster = Adamantine/Greasy

| streak = White

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| gravity = 4.77 (Calculated)

| density = 4.77 g/cm3 (Calculated)

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| opticalprop = Biaxial (+), a=2.004, b=2.01, g=2.024, bire=0.0200

| refractive = nα = 2.004 nβ = 2.010 nγ = 2.024

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| 2V = 67° (calculated)

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Challacolloite, KPb₂Cl₅, is a rare halide mineral. It crystallizes in the monoclinic system (with space group P2₁/c{{cite journal |last1=Mitolo |first1=D. |last2=Pinto |first2=D. |last3=Garavelli |first3=A. |last4=Bindi |first4=L. |last5=Vurro |first5=F. |title=The role of the minor substitutions in the crystal structure of natural challacolloite, KPb2Cl5, and hephaistosite, TlPb2Cl5, from Vulcano (Aeolian Archipelago, Italy) |journal=Mineralogy and Petrology |date=May 2009 |volume=96 |issue=1–2 |pages=121–128 |doi=10.1007/s00710-008-0041-2|bibcode=2009MinPe..96..121M |s2cid=128797167 }}) and occurs as white fumarolic encrustations on lava. It occurs as intergrowths with cotunnite.[http://webmineral.com/data/Challacolloite.shtml Webmineral]

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.[http://www.mindat.org/min-27422.html Mindat with location data] It was recognized as a valid mineral species by the IMA (International Mineralogical Association) in 2005.

Artificially grown KPb₂Cl₅ crystals are used for lasers.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 [http://www.schweizerbart.de/resources/downloads/paper_previews/57464.pdf pdf]