Mineralogy Database

Arnhemite Mineral Data

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General Arnhemite Information

Help on Chemical  Formula: Chemical Formula: (K,Na)2Mg2(P2O7)•5(H2O)
Help on Composition: Composition: Molecular Weight = 620.94 gm
   Potassium   17.50 %  K    21.09 % K2O
   Sodium       3.37 %  Na    4.54 % Na2O
   Calcium      0.97 %  Ca    1.35 % CaO
   Magnesium    6.89 %  Mg   11.42 % MgO
   Manganese    0.18 %  Mn    0.23 % MnO
   Zinc         0.11 %  Zn    0.13 % ZnO
   Iron         0.27 %  Fe    0.35 % FeO
   Phosphorus  20.10 %  P    46.06 % P2O5
   Hydrogen     1.66 %  H    14.83 % H2O
   Oxygen      48.96 %  O
              ______        ______ 
              100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: K2.78Na0.91Mg1.76Ca0.15Fe2+0.03Mn2+0.02Zn0.01P4.03O13.89�5.11(H2O)
Help on Environment: Environment: Occurs as flakes that form aggregates making up the principal component of a thin layer of white, friable slag in the profile of cave-floor soil.
Help on IMA Status: IMA Status: Not Approved IMA
Help on Locality: Locality: Arnhem Cave, Namibia. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named after it's locality.
 

Arnhemite Crystallography

Help on Axial Ratios: Axial Ratios: a:c = 1:1.51446
Help on Cell Dimensions: Cell Dimensions: a = 11.06, c = 16.75, Z = 4; V = 1,774.42 Den(Calc)= 2.32
Help on Crystal System: Crystal System: Hexagonal Space Group: Unk
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 16.7(1)(001 ), 2.761(0.25)(220 ), 8.33(0.15)(011 ),2.3(0.1)(224,042), 2.216(0.05)(126 ), 4.616(0.05)(112 ), 3.184(0.05)(030 ),
 

Physical Properties of Arnhemite

Help on Cleavage: Cleavage: {001} Perfect
Help on Color: Color: White.
Help on Density: Density: 2.33 - 2.35, Average = 2.34
Help on Diaphaneity: Diaphaneity: Transparent
Help on Fracture: Fracture: Friable - The crumbly disintegration of earthy materials or highly fractured minerals.
Help on Luster: Luster: Pearly
Help on Streak: Streak: white
 

Optical Properties of Arnhemite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= -0.029 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= -0.038 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2196,KPDmeas= 0.2177,KC= 0.2117
Ncalc = 1.49 - 1.5
Help on Optical Data: Optical Data: Uniaxial (-), e=1.503, w=1.516, bire=0.0130.
 

Calculated Properties of Arnhemite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=2.35 gm/cc
note: Specific Gravity of Arnhemite =2.34 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.0072609178
Boson Index = 0.9927390822
Help on Photoelectric: Photoelectric: PEArnhemite = 3.22 barns/electron
U=PEArnhemite x relectron= 7.54 barns/cc.
Help on Radioactivity: Radioactivity:

GRapi = 253.16 (Gamma Ray American Petroleum Institute Units)
Concentration of Arnhemite per GRapi unit = 0.40 (%)

Estimated Radioactivity from Arnhemite - barely detectable

 

Arnhemite Classification

Help on  Dana Class: Dana Class: 37.00.00.00 (37)Phosphate Minerals
  (37.00)Without Dana Classification Numbers
  (37.00.00)Phosphate, Thermocaca Series
 
37.00.00.00 Arnhemite* (K,Na)2Mg2(P2O7)•5(H2O) Unk Hex
 
37.00.00.00 Arsenowaylandite* BiAl3(AsO4)2(OH)6 R 3m 3 2/m
 
37.00.00.00 Auroantimonate* AuSbO3 Ortho ? Ortho
 
37.00.00.00 Barium-zinc-alumopharmacosiderite* (Ba,K)0.5(Zn,Cu)0.5(Al,Fe)4(AsO4)3•5(H2O) I 42m 4 2m
 
37.00.00.00 Chernovite-(Ce)* (Ce,Y)(AsO4) I 41/amd 4/m 2/m 2/m
 
37.00.00.00 Churchite-(Dy)* (Dy,Sm,Gd,Nd)(PO4)•2(H2O) Mono
 
37.00.00.00 Gengenbachite KFe3(H2PO4)2(HPO4)4•6H2OorKFe3H8(PO4)6•6H2O P 63mc 6mm
 
37.00.00.00 IMA2008-063 Pb[Zn0.25,[]0.75]Fe3H(AsO4)2(OH)6 C 2/c 2/m
 
37.00.00.00 IMA2009-005 (Y,Ca,REE)5[(Si,P)O4]3F P 63/m 6/m 2/m 2/m
 
37.00.00.00 IMA2009-016 Cu4H(AsO4)2(OH)3•H2O P1 1
 
37.00.00.00 Kerstenite? PbSeO4(?) P nma 2/m 2/m 2/m
 
37.00.00.00 Krasnoselskite* CoWO4 P 2/c 2/m
 
37.00.00.00 Laubmannite? Fe3Fe6(PO4)4(OH)12 Unk Ortho
 
37.00.00.00 Oxiberaunite* (Fe,Mn)Fe5(PO4)4O(OH)4•6(H2O) Mono
 
37.00.00.00 Parwanite (Na,K)(Mg,Ca)4Al8(PO4)8(CO3)(OH)7•30H2O P 2, Pm, P 2/m, P 21, Mono
 
37.00.00.00 Pyrocoproite* (Mg(K,Na))2P2O7 Unk Mono
 
37.00.00.00 Pyrophosphite* K2CaP2O7 P 21/n 2/m
 
37.00.00.00 Zinclavendulan? NaCa(Zn,Cu)5(AsO4)4Cl•4-5(H2O) Unk Ortho
Help on  Strunz Class: Strunz Class: 08.FC.20 08 - PHOSPHATES, ARSENATES, VANADATES
  08.F - Polyphosphates, Polyarsenates, [4]-Polyvanadates
  08.FC -Polyphosphates, etc., with H2O only
 
08.FC.20 Arnhemite* (K,Na)2Mg2(P2O7)•5(H2O) Unk Hex
 

Other Arnhemite Information

Help on References: References: NAME( AmMin, v84:193) PHYS. PROP.(Am.Min.,Vol.84,p193,1999) OPTIC PROP.(AmMin, v84:193)
Help on See Also: See Also: Links to other databases for Arnhemite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - Mineralienatlas (Deutsch)
8 - Online Mineral Museum
9 - QUT Mineral Atlas
10 - Ruff.Info

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Print or Cut-and-Paste your Arnhemite Specimen Label here :

Arnhemite

(K,Na)2Mg2(P2O7)•5(H2O)
Dana No: 37.00.00.00 Strunz No: 08.FC.20
Locality:

 

Notes:

 

 
   
 


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