Paralaurionite

Paralaurionite
Platey clear paralaurionite crystals from slag in the Thorikos area, Lavrion, Attica, Greece
General
CategoryHalide mineral
Formula
(repeating unit)		PbCl(OH)
IMA symbolPlri[1]
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[2][3][4][5]

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.[6] The name is derived from para-, the Greek for "near", and laurionite, because of its polymorphic relationship to it.[4] Bright, yellow tips of thorikosite can form on paralaurionite crystals and paralaurionite may also be intergrown with mendipite.[7][8]

Occurrence

It was first described in 1899 for an occurrence in slag in Laurium, Attica, Greece.[3] In 1952 an occurrences of it was reported from the Mammoth Mine, Arizona.[9]

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.[3]

References

  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 Handbook of Mineralogy
  4. ^ a b Paralaurionite on Mindat.org
  5. ^ Paralaurionite on Webmineral
  6. ^ Mineralogical magazine. Mineralogical Society, HighWire Press. 1 January 2006. pp. 643–8. Retrieved 26 January 2012.
  7. ^ The Mineralogical record. 1986. pp. 185–88. Retrieved 26 January 2012.
  8. ^ Williams, Peter A. (August 1990). Oxide zone geochemistry. E. Horwood. pp. 262–4. ISBN 978-0-13-647553-8. Retrieved 26 January 2012.
  9. ^ 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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