Polyhalite Mineral Data
General Polyhalite Information
Chemical Formula:
K2Ca2Mg(SO4)4•2(H2O)
Composition:
Molecular Weight = 602.94 gm
Potassium 12.97 % K 15.62 % K2 O
Calcium 13.29 % Ca 18.60 % CaO
Magnesium 4.03 % Mg 6.68 % MgO
Hydrogen 0.67 % H 5.98 % H2 O
Sulfur 21.27 % S 53.12 % SO3
Oxygen 47.76 % O
______ ______
100.00 % 100.00 % = TOTAL OXIDE
Empirical Formula:
K2 Ca2 Mg(SO4 )4 •2(H2 O)
Environment:
Sedimentary marine evaporite deposits.
IMA Status:
Valid Species (Pre-IMA) 1818
Locality:
Potash beds near Carlsbad, New Mexico. Link to MinDat.org Location Data.
Name Origin:
From the Greek, polys, meaning "much" and hals, meaning "salt." in allusion to the many salt components in the formulae..
Name Pronunciation:
Polyhalite + Pronunciation
Synonym:
ICSD 6303
PDF 21-982
Polyhalite Image
Images:
Polyhalite Crystallography
Axial Ratios:
a:b:c =0.7158:1:0.4654
Cell Dimensions:
a = 11.69, b = 16.33, c = 7.6, Z = 4; alpha = 91.6°, beta = 90°, gamma = 91.9° V = 1,449.46 Den(Calc)= 2.76
Crystal System:
Triclinic Space Group: P 1 ,P1
X Ray Diffraction:
By Intensity(I/Io ): 2.9(1), 3.18(0.7), 2.85(0.16),
Forms:
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Forms:
( 0 1 0)
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Physical Properties of Polyhalite
Cleavage:
{101} Perfect
Color:
Colorless, Gray, Gray white, White, Pink.
Density:
2.77 - 2.78, Average = 2.77
Diaphaneity:
Transparent to Translucent
Fracture:
Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.
Habit:
Massive - Fibrous - Distinctly fibrous fine-grained forms.
Habit:
Massive - Lamellar - Distinctly foliated fine-grained forms.
Hardness:
2.5-3.5 - Finger Nail-Copper Penny
Luster:
Vitreous (Glassy)
Streak:
white
Optical Properties of Polyhalite
Gladstone-Dale:
CI meas = -0.019 (Superior) - where the CI = (1-KPDmeas /KC ) CI calc = -0.024 (Excellent) - where the CI = (1-KPDcalc /KC )
KPDcalc = 0.2022,KPDmeas = 0.2011,KC = 0.1974 Ncalc = 1.54 - 1.55
Optical Data:
Biaxial (-), a=1.546-1.548, b=1.558-1.562, g=1.567, bire=0.0190-0.0210, 2V(Calc)=60-80, 2V(Meas)=60-62.
Pleochroism (x):
colorless.
Pleochroism (y):
colorless.
Pleochroism (z):
colorless.
Calculated Properties of Polyhalite
Electron Density:
Bulk Density (Electron Density)=2.78 gm/cc note: Specific Gravity of Polyhalite =2.78 gm/cc.
Fermion Index:
Fermion Index = 0.0060518431 Boson Index = 0.9939481569
Photoelectric:
PEPolyhalite = 4.30 barns/electronU=PEPolyhalite x r electron = 11.94 barns/cc.
Radioactivity:
GRapi = 187.47 (Gamma Ray American Petroleum Institute Units)
Concentration of Polyhalite per GRapi unit = 0.53 (%)
Estimated Radioactivity from Polyhalite - barely detectable
Polyhalite Classification
Dana Class:
29.04.05.01 (29) Hydrated Acid and Sulfates
(29.04) where (A+)2 Bn (XO4)p � x(H2O)
(29.04.05) Dana Group
29.04.05.01 Polyhalite K2Ca2Mg(SO4)4•2(H2O) P 1 ,P1 Tri
29.04.05.02 Leightonite K2Ca2Cu(SO4)4•2(H2O) C 2/c 2/m
Strunz Class:
07.CC.65 07 - SULFATES (SELENATES, TELLURATES)
07.C - Sulfates (selenates, etc.) without Additional Anions, with H2O
07.CC -With medium-sized and large cations
07.CC.65 Polyhalite K2Ca2Mg(SO4)4•2(H2O) P 1 ,P1 Tri
Other Polyhalite Information
References:
NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32)
See Also:
Links to other databases for Polyhalite :
1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - EUROmin Project
5 - Ecole des Mines de Paris
6 - GeoScienceWorld
7 - Google Images
8 - Google Scholar
9 - Handbook of Mineralogy (MinSocAm)
10 - Handbook of Mineralogy (UofA)
11 - MinDAT
12 - Mineralienatlas (Deutsch)
13 - Online Mineral Museum
14 - QUT Mineral Atlas
15 - Ruff.Info
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Polyhalite
K2Ca2Mg(SO4)4•2(H2O)
Dana No: 29.04.05.01 Strunz No: 07.CC.65
Locality:
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