Pickeringite Mineral Data

Pickeringite Mineral Data +

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General Pickeringite Information

Chemical Formula:

MgAl2(SO4)4·22(H2O)

Composition:

Molecular Weight = 858.86 gm

Magnesium 2.83 % Mg 4.69 % MgO

Aluminum 6.28 % Al 11.87 % Al₂O₃

Hydrogen 5.16 % H 46.15 % H₂O

Sulfur 14.93 % S 37.29 % SO₃

Oxygen 70.79 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

MgAl₂(SO₄)₄·22(H₂O)

IMA Status:

Valid Species (Pre-IMA) 1844

Locality:

Link to MinDat.org Location Data.

Name Origin:

Named after J. Pickering (1777-1846).

Synonym:

Magnesia Alum

Pickeringite Image

Images:

Click Here for Larger Pickeringite Image

Pickeringite Magnesioaubertite

Comments: Aqua crystalline magnesioaubertite with white pickeringite.
Location: Grotto di Faraglione, Vulcano, Sicily, Italy. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Images:

Pickeringite

Comments: Radiating fibrous pickeringite.
Location: Patagonia, Santa Cruz County, Arizona, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Pickeringite Crystallography

Axial Ratios:

a:b:c =0.8595:1:0.2553

Cell Dimensions:

a = 20.8, b = 24.2, c = 6.18, Z = 4; beta = 95° V = 3,098.93 Den(Calc)= 1.84

Crystal System:

Monoclinic - SphenoidalH-M Symbol (2) Space Group: P 2

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 4.82(1), 3.51(0.9), 4.32(0.35),

Crystal Structure:

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drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
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Quartieri S , Triscari M , Viani A , European Journal of Mineralogy , 12 (2000) p.1131-1138, Crystal structure of the hydrated sulphate pickeringite (MgAl2(SO4)4.22H2O):, X-ray powder diffraction study

Physical Properties of Pickeringite

Cleavage:

[010] Indistinct

Color:

Colorless, Yellowish white, Reddish white, Greenish white.

Density:

1.8 - 1.85, Average = 1.82

Diaphaniety:

Transparent to translucent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habit:

Encrustations - Forms crust-like aggregates on matrix.

Habit:

Fibrous - Crystals made up of fibers.

Habit:

Reniform - "Kidney like" in shape (e.g.. hematite).

Hardness:

1.5-2 - Talc-Gypsum

Luminescence:

None.

Luster:

Silky

Streak:

white

Optical Properties of Pickeringite

Gladstone-Dale:

CI meas= -0.023 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= -0.015 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2607,KPDmeas= 0.2628,KC= 0.2569

Optical Data:

Biaxial (-), a=1.476, b=1.48, g=1.483, bire=0.0070, 2V(Calc)=80, 2V(Meas)=60. Dispersion none.

Calculated Properties of Pickeringite

Electron Density:

r_electron=1.93 gm/cc
note: r_Pickeringite=1.84 gm/cc.

Fermion Index

Fermion Index = 0.00429
Boson Index = 0.99571

Photoelectric:

PE_Pickeringite= 1.27 barns/electron
U=PE_Pickeringite x r_electron= 2.45 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Pickeringite is Not Radioactive

Pickeringite Classification

Dana Class:

29.7.3.1 (29)Hydrated Acid and Sulfates

(29.7)where A (B)2 (XO4)4 · x(H2O)

(29.7.3)Halotrichite Group (Monoclinic with 22 H2O)

29.7.3.1 Pickeringite MgAl2(SO4)4·22(H2O) P 2 2

29.7.3.2 Halotrichite FeAl2(SO4)4·22(H2O) P 2 2

29.7.3.3 Apjohnite MnAl2(SO4)4·22(H2O) P 2₁/c 2/m

29.7.3.4 Dietrichite (Zn,Fe,Mn)Al2(SO4)4·22(H2O) P 2₁/c 2/m

29.7.3.5 Bilinite FeFe2(SO4)4·22(H2O) P 2₁/c 2/m

29.7.3.6 Redingtonite (Fe,Mg,Ni)(Cr,Al)2(SO4)4·22(H2O) Mono

29.7.3.7 Wupatkiite (Co,Mg,Ni)Al2(SO4)4·22(H2O) P 2₁/c 2/m

Strunz Class:

VI/C.12-10 VI - Sulfates,Chromates,Molybdates and Tungstates

VI/C - Water-bearing sulfates without unfamiliar anions. cations of medium and very big size

VI/C.12 - Halotrichite group, Pickeringite - Bilinite

VI/C.12-10 Pickeringite MgAl2(SO4)4·22(H2O) P 2 2

VI/C.12-12 Wupatkiite (Co,Mg,Ni)Al2(SO4)4·22(H2O) P 2₁/c 2/m

VI/C.12-20 Halotrichite FeAl2(SO4)4·22(H2O) P 2 2

VI/C.12-30 Apjohnite MnAl2(SO4)4·22(H2O) P 2₁/c 2/m

VI/C.12-40 Dietrichite (Zn,Fe,Mn)Al2(SO4)4·22(H2O) P 2₁/c 2/m

VI/C.12-50 Redingtonite (Fe,Mg,Ni)(Cr,Al)2(SO4)4·22(H2O) Mono

VI/C.12-60 Bilinite FeFe2(SO4)4·22(H2O) P 2₁/c 2/m

Other Pickeringite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)

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Pickeringite

MgAl2(SO4)4·22(H2O)
Dana No: 29.7.3.1 Strunz No: VI/C.12-10
Locality:

Notes: