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Sewardite Mineral Data

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General Sewardite Information

Help on Chemical  Formula: Chemical Formula: CaFe+++2(AsO4)2(OH)2
Help on Composition: Composition: Molecular Weight = 464.68 gm
   Calcium    8.62 %  Ca   12.07 % CaO
   Zinc       1.41 %  Zn    1.75 % ZnO
   Iron      22.83 %  Fe   32.65 % Fe2O3
   Arsenic   32.25 %  As   49.46 % As2O5
   Hydrogen   0.46 %  H     4.07 % H2O
   Oxygen    34.43 %  O
            ______        ______ 
            100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: CaFe3+1.9Zn0.1(AsO4)2(OH)1.9(H2O)0.1
Help on Environment: Environment: Intergrown with ferrilotharmeyerite and another unknown. (Ca-dominant analogue of carminite; structure)
Help on IMA Status: IMA Status: Approved IMA 2002 (Dana # Added)
Help on Locality: Locality: 31st Level, Tsumeb mine, Tsumeb, Namibia. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named for Terry Maxwell Seward (1940-) who collected the mineral.
Help on Synonym: Synonym: IMA2001-054

Sewardite Image

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Comments: Photomicrograph of an isolated fragment of red sewardite as well as a fragment in green to black botryoidal matrix.
Location: Single specimen of gangue collected from the 31st level of the Tsumeb mine, Tsumeb, Namibia. Scale: See Image.
© Canadian Mineralogist

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Comments: Deep red, micaceous sewardite crystals mistakenly identified as carminite.
Location: Benjamin Hill, Sonora, Mexico. Scale: Picture size 1 cm.
© Tom Loomis / Dakota Matrix

Sewardite Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =2.2142:1:1.6318
Help on Cell Dimensions: Cell Dimensions: a = 16.461, b = 7.434, c = 12.131, Z = 8; V = 1,484.48 Den(Calc)= 4.16
Help on Crystal System: Crystal System: Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: C ccm
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 3.167(1)(022), 2.503(0.9)(422,314), 4.874(0.9)(202),2.919(0.7)(511), 3.389(0.6)(220), 1.775(0.5)(026), 2.988(0.5)(313), 3.015(0.5)(510), 3.473(0.5)(113),

Physical Properties of Sewardite

Help on Cleavage: Cleavage: {100} Imperfect, {011} Imperfect
Help on Color: Color: Dark red, Lighter red orange.
Help on Diaphaneity: Diaphaneity: Translucent
Help on Fracture: Fracture: Splintery - Thin, elongated fractures produced by intersecting good cleavages or partings (e.g. hornblende).
Help on Habit: Habit: Aggregates - Made of numerous individual crystals or clusters.
Help on Habit: Habit: Anhedral Grains - Granular minerals without the expression of crystal shapes
Help on Habit: Habit: Platy - Sheet forms (e.g. micas).
Help on Hardness: Hardness: 3.5 - Copper Penny
Help on Luster: Luster: Vitreous (Glassy)
Help on Streak: Streak: reddish brown

Optical Properties of Sewardite

Help on Optical Data: Optical Data: NCalc= 1.94 - from Gladstone-Dale relationship (KC = 0.2249) where Ncalc=Dcalc*KC+1
Help on RL Anisotrophism: RL Anisotrophism: None.
Help on RL Bireflectance: RL Bireflectance: Weak.
Help on RL Color: RL Color: Light bluish gray with bright pink to red internal reflections.
Help on RL Pleochroism: RL Pleochroism: None.
Help on Reflectivity Reflectivity
Standardized Intensity (100%) Reflection Spectra of Sewardite in Air
λ R1 R2  ∑ R1(λ)   ∑ R2(λ) 
 460 nm   10.12   10.71 
 540 nm    9.53   10.07 
 580 nm    9.30    9.98 
 640 nm    8.99    9.66 
Calculated Relative Intensity Colors of Sewardite in Air
   0% 100% 200% 300% 400% 500% 600% 700% 800% 900% 950%

Calculated Properties of Sewardite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=3.95 gm/cc
note: Specific Gravity of Sewardite =4.16 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.0057003424
Boson Index = 0.9942996576
Help on Photoelectric: Photoelectric: PESewardite = 30.83 barns/electron
U=PESewardite x rElectron Density= 121.72 barns/cc.
Help on Radioactivity: Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Sewardite is Not Radioactive

Sewardite Classification

Help on  Dana Class: Dana Class: (41)Anhydrous Phosphates, etc. Containing Hydroxyl or Halogen
  (41.10)where (A++ B++)3 (XO4)2 Zq
  (41.10.06)Carminite Group Carminite PbFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m Sewardite! CaFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m
Help on  Strunz Class: Strunz Class: 08.BH.30 08 - PHOSPHATES, ARSENATES, VANADATES
  08.B - Phosphates, etc. with Additional Anions, without H2O
  08.BH -With medium-sized and large cations, (OH,etc.):RO4 = 1:1
08.BH.30 Carminite PbFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m
08.BH.30 Sewardite! CaFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m

Other Sewardite Information

Help on References: References: NAME( AmMin, v 88, p 1178) PHYS. PROP.(AmMin, v 88, p 1178) OPTIC PROP.(AmMin, v 88, p 1178)
Help on See Also: See Also: Links to other databases for Sewardite :
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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Dana No: Strunz No: 08.BH.30





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