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Johnwalkite Mineral Data

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General Johnwalkite Information

Help on Chemical  Formula: Chemical Formula: K(Mn++,Fe+++,Fe++)2(Nb,Ta)(PO4)2O2((H2O),OH)2
Help on Composition: Composition: Molecular Weight = 480.93 gm
   Potassium    7.32 %  K     8.81 % K2O
   Magnesium    0.51 %  Mg    0.84 % MgO
   Tantalum     3.76 %  Ta    4.59 % Ta2O5
   Manganese   11.42 %  Mn   14.75 % MnO
   Niobium     15.45 %  Nb   22.11 % Nb2O5
   Iron         9.29 %  Fe   13.28 % Fe2O3
   Phosphorus  12.24 %  P    28.04 % P2O5
   Hydrogen     0.75 %  H     6.74 % H2O
   Oxygen      39.26 %  O
              ______        ______ 
              100.00 %       99.17 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: K0.9Mn2+Fe3+0.7Mg0.1Nb0.8Ta0.1Fe3+0.1O2(PO4)1.9(H2O)1.4(OH)0.8
Help on Environment: Environment: Secondary mineral derived from the dissolution of triphylite-lithiophilite and columbite-tantalite in a complex granite pegmatite.
Help on IMA Status: IMA Status: Approved IMA 1986
Help on Locality: Locality: Expectation pegmatite at the Champion mine, about 2.5 km southeast of Keystone, Pennington County, South Dakota, USA. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named for Richard JOHNson (1936-1998) and Frank WALKup (1943-1993), mineral preparators, National Museum of Natural History, Washington, D. C., USA.
Help on Name Pronunciation: Name Pronunciation: Johnwalkite + Pronunciation Say JOHNWALKITE

Johnwalkite Image

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Comments: Fragment of translucent johnwalkite.
Location: Champion Mine, Keystone District, Pennington Co., South Dakota, USA. Scale: Crystal length 1 mm.
© Jeff Weissman / Photographic Guide to Mineral Species

Johnwalkite Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =0.7498:1:0.6487
Help on Cell Dimensions: Cell Dimensions: a = 7.516, b = 10.023, c = 6.502, Z = 2; V = 489.81 Den(Calc)= 3.26
Help on Crystal System: Crystal System: Orthorhombic - Pyramidal H-M Symbol (mm2) Space Group: Pb21m
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 6.01(1), 3.005(0.8), 3.054(0.7),

Physical Properties of Johnwalkite

Help on Cleavage: Cleavage: {001} Good, {100} Good
Help on Color: Color: Dark reddish brown, Reddish brown.
Help on Density: Density: 3.4
Help on Diaphaneity: Diaphaneity: Transparent to Translucent
Help on Fracture: Fracture: Brittle - Generally displayed by glasses and most non-metallic minerals.
Help on Habit: Habit: Aggregates - Made of numerous individual crystals or clusters.
Help on Habit: Habit: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Help on Habit: Habit: Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)
Help on Hardness: Hardness: 4 - Fluorite
Help on Luster: Luster: Vitreous (Glassy)
Help on Streak: Streak: greenish yellow

Optical Properties of Johnwalkite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= -0.001 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.044 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2404,KPDmeas= 0.2305,KC= 0.2303
Ncalc = 1.75 - 1.78
Help on Optical Data: Optical Data: Biaxial (+), a=1.748, b=1.763, g=1.84, bire=0.0920, 2V(Calc)=50, 2V(Meas)=53.
Help on Pleochroism (x): Pleochroism (x): blue green.
Help on Pleochroism (y): Pleochroism (y): yellow or pale brown.
Help on Pleochroism (z): Pleochroism (z): brown.

Calculated Properties of Johnwalkite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=3.26 gm/cc
note: Specific Gravity of Johnwalkite =3.40 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.0026776959
Boson Index = 0.9973223041
Help on Photoelectric: Photoelectric: PEJohnwalkite = 70.30 barns/electron
U=PEJohnwalkite x relectron= 229.33 barns/cc.
Help on Radioactivity: Radioactivity:

GRapi = 101.29 (Gamma Ray American Petroleum Institute Units)
Concentration of Johnwalkite per GRapi unit = 0.99 (%)

Estimated Radioactivity from Johnwalkite - barely detectable


Johnwalkite Classification

Help on  Dana Class: Dana Class: (42)Hydrated Phosphates, etc., Containing Hydroxyl or Halogen
  (42.07)where (AB)5 (XO4)3 Zq � x(H2O)
  (42.07.11)Olmsteadite Group Olmsteadite KFe2(Nb,Ta)(PO4)2O2•2(H2O) Pb21m mm2 Johnwalkite K(Mn,Fe,Fe)2(Nb,Ta)(PO4)2O2((H2O),OH)2 Pb21m mm2
Help on  Strunz Class: Strunz Class: 08.DJ.05 08 - PHOSPHATES, ARSENATES, VANADATES
  08.D - Phosphates, etc
  08.DJ -With large and medium-sized cations, (OH, etc.):RO4 = 1:l
08.DJ.05 Johnwalkite K(Mn,Fe,Fe)2(Nb,Ta)(PO4)2O2((H2O),OH)2 Pb21m mm2
08.DJ.05 Olmsteadite KFe2(Nb,Ta)(PO4)2O2•2(H2O) Pb21m mm2

Other Johnwalkite Information

Help on References: References: NAME( AntBidBlaNic4) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic4)
Help on See Also: See Also: Links to other databases for Johnwalkite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - MinDAT
10 - Mineralienatlas (Deutsch)
11 - Online Mineral Museum
12 - QUT Mineral Atlas
13 - Ruff.Info

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Dana No: Strunz No: 08.DJ.05





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