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Olmsteadite Mineral Data

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General Olmsteadite Information

Help on Chemical  Formula: Chemical Formula: KFe++2(Nb,Ta)(PO4)2O2•2(H2O)
Help on Composition: Composition: Molecular Weight = 523.68 gm
   Potassium    7.47 %  K     8.99 % K2O
   Tantalum     8.64 %  Ta   10.55 % Ta2O5
   Niobium     13.31 %  Nb   19.03 % Nb2O5
   Iron        21.33 %  Fe   27.44 % FeO
   Phosphorus  11.83 %  P    27.11 % P2O5
   Hydrogen     0.77 %  H     6.88 % H2O
   Oxygen      36.66 %  O
              ______        ______ 
              100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: KFe2+2Nb0.75Ta0.25(PO4)2O2•2(H2O)
Help on Environment: Environment: Found in Nb-Ta bearing pegmatites.
Help on IMA Status: IMA Status: Approved IMA 1976
Help on Locality: Locality: Big Chief pegmatite, near Glendale, Pennington County, South Dakota, USA. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named for Milo Olmstead, micromount mineral collector, Rapid City, South Dakota, USA.
Help on Name Pronunciation: Name Pronunciation: Olmsteadite + Pronunciation Say OLMSTEADITE
Help on Synonym: Synonym: ICSD 12138
  PDF 35-633

Olmsteadite Image

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Comments: Dark brown crystals of olmsteadite with jahnsite on siderite.
Location: Big Chief mine, Keystone, Penningtion County, South Dakota, USA. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Olmsteadite Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =0.7512:1:0.6492
Help on Cell Dimensions: Cell Dimensions: a = 7.512, b = 10, c = 6.492, Z = 2; V = 487.68 Den(Calc)= 3.57
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): 6.006(1), 3.003(0.7), 3.047(0.6),

Physical Properties of Olmsteadite

Help on Cleavage: Cleavage: {100} Good, {001} Good
Help on Color: Color: Brown, Reddish brown, Black.
Help on Density: Density: 3.31 - 3.36, Average = 3.33
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: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Help on Hardness: Hardness: 4 - Fluorite
Help on Luster: Luster: Subadamantine
Help on Streak: Streak: olive green

Optical Properties of Olmsteadite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= -0.116 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.042 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.218,KPDmeas= 0.2334,KC= 0.2091
Ncalc = 1.69 - 1.75
Help on Optical Data: Optical Data: Biaxial (+), a=1.725-1.765, b=1.755-1.775, g=1.815-1.835, bire=0.0700-0.0900, 2V(Calc)=46-74, 2V(Meas)=60.
Help on Pleochroism (x): Pleochroism (x): blue green.
Help on Pleochroism (y): Pleochroism (y): yellow.
Help on Pleochroism (z): Pleochroism (z): brown.

Calculated Properties of Olmsteadite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=3.41 gm/cc
note: Specific Gravity of Olmsteadite =3.57 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.0047181274
Boson Index = 0.9952818726
Help on Photoelectric: Photoelectric: PEOlmsteadite = 120.73 barns/electron
U=PEOlmsteadite x relectron= 411.53 barns/cc.
Help on Radioactivity: Radioactivity:

GRapi = 102.84 (Gamma Ray American Petroleum Institute Units)
Concentration of Olmsteadite per GRapi unit = 0.97 (%)

Estimated Radioactivity from Olmsteadite - barely detectable


Olmsteadite 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 Olmsteadite Information

Help on References: References: NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Dana8)
Help on See Also: See Also: Links to other databases for Olmsteadite :
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 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Dana No: Strunz No: 08.DJ.05





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