Paralaurionite

Paralaurionite is a colorless mineral consisting of a basic lead chloride PbCl(OH) that is dimorphous with laurionite. It is a member of the matlockite group.[5] The name is derived from para-, the Greek for "near", and laurionite, because of its polymorphic relationship to it.[3] Bright, yellow tips of thorikosite can form on paralaurionite crystals and paralaurionite may also be intergrown with mendipite.[6][7]

Paralaurionite
Platey clear paralaurionite crystals from slag in the Thorikos area, Lavrion, Attica, Greece
General
CategoryHalide mineral
Formula
(repeating unit)		PbCl(OH)
Strunz classification3.DC.05
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 10.865(4) Å,
b = 4.006(2) Å,
c = 7.233(3) Å;
β = 117.24(4)°; Z = 4
Identification
ColorColorless, white, pale greenish, yellowish, yellow-orange, rarely violet
Crystal habitElongated tabular crystals
TwinningContact twinning on {100}
CleavagePerfect on {001}
TenacityFlexible, non-elastic
Mohs scale hardness3
LusterSubadamantine
DiaphaneityTransparent to translucent
Specific gravity6.05–6.15
Optical propertiesBiaxial (-)
Refractive indexnα = 2.050 nβ = 2.150 nγ = 2.200
Birefringenceδ = 0.150
PleochroismVisible
References[1][2][3][4]

Occurrence

It was first described in 1899 for an occurrence in slag in Laurium, Attica, Greece.[2] In 1952 an occurrences of it was reported from the Mammoth Mine, Arizona.[8]

It occurs in lead bearing slag which has been exposed to seawater. It also occurs in polymetallic ore deposits. It occurs associated with laurionite, penfieldite, fiedlerite, phosgenite in slag deposits; and with leadhillite, matlockite, cerussite, hydrocerussite, diaboleite and wherryite in the Mammoth mine location.[2]

References
  1. Mineralienatlas
  2. Handbook of Mineralogy
  3. Paralaurionite on Mindat.org
  4. Paralaurionite on Webmineral
  5. Mineralogical magazine. Mineralogical Society, HighWire Press. 1 January 2006. pp. 643–8. Retrieved 26 January 2012.
  6. The Mineralogical record. 1986. pp. 185–88. Retrieved 26 January 2012.
  7. Williams, Peter A. (August 1990). Oxide zone geochemistry. E. Horwood. pp. 262–4. ISBN 978-0-13-647553-8. Retrieved 26 January 2012.
  8. Mineralogical Society (Great Britain) (1952). The Mineralogical magazine and journal of the Mineralogical Society. Mineralogical Society. pp. 341–2. Retrieved 26 January 2012.
Unusually large crystals of Paralaurionite, Touissit, Oujda-Angad Province, Morocco. Size: 6 x 5.5 x 5 cm.
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