Pickeringite

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Pickeringite
Pickeringite-87353.jpg
Cobalt rich pickeringite from the Northern Slanské Mts, Prešov Region, Slovakia
General
CategorySulfate mineral
Formula
(repeating unit)
MgAl2(SO4)4·22(H2O)
IMA symbolPkg[1]
Strunz classification7.CB.85
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/c
Unit cella = 20.8, b = 24.2,
c = 6.18 [Å]; β = 95°; Z = 4
Identification
ColorColorless, white; may be shades of yellow, green, or red due to impurities
Crystal habitRarely as acicular crystals, radial or matted aggregates; typically as incrustations and efflorescences
CleavagePoor on {010}
FractureConchoidal
Mohs scale hardness1.5
LusterVitreous
DiaphaneitySemitransparent
Specific gravity1.73–1.79
Optical propertiesBiaxial (-)
Refractive indexnα = 1.476 nβ = 1.480 nγ = 1.483
Birefringenceδ = 0.007
2V angleMeasured: 60°
SolubilityCompletely soluble in water
Common impuritiesMay contain iron, manganese or cobalt
References[2][3][4][5]

Pickeringite is a magnesium aluminium sulfate mineral with formula MgAl2(SO4)4·22(H2O). It forms a series with halotrichite.

It forms as an alteration product of pyrite in aluminium rich rocks and in coal seams. It also occurs in pyrite rich hydrothermal ore deposits in arid regions. It forms in fumaroles and in caves. It occurs with kalinite, alunogen, epsomite, melanterite, copiapite and gypsum.[2]

It was first described in 1844 for an occurrence in Cerros Pintados, Pampa del Tamarugal, Iquique Province, Tarapacá Region, Chile. It was named for American linguist and philologist John Pickering (1777–1846).[3]

Pickeringite in the Natural History Museum

References[edit]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85: 291–320.
  2. ^ a b Handbook of Mineralogy
  3. ^ a b Pickeringite on Mindat.org
  4. ^ Pickeringite data on Webmineral
  5. ^ Mineralienatlas