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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Sewardite

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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Sewardite

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 - DipyramidalH-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),
Click Here for Large Sewardite Structure Window Crystal Structure:

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Roberts A C , Cooper M A , Hawthorne F C , Criddle A J , Stirling J A R , The Canadian Mineralogist , 40 (2002) p.1191-1198, Sewardite, CaFe2(AsO4)(OH)2, the Ca-analogue of carminite,, from Tsumeb, Namibia: Description and crystal structure, Locality: Tsumeb, Namibia

 

Physical Properties of Sewardite

Help on Cleavage: Cleavage: [100] Imperfect, [011] Imperfect
Help on Color: Color: Dark red, Lighter red orange.
Help on Diaphaniety: Diaphaniety: 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
Relative
Intensity		    0% 100% 200% 300% 400% 500% 600% 700% 800% 900% 950%
R1                      
R2                      
 

Calculated Properties of Sewardite

Help on Electron Density: Electron Density:

relectron=3.95 gm/cc
note: rSewardite =4.16 gm/cc.
Help on Fermion Index Fermion Index Fermion Index = 0.0057
Boson Index = 0.9943
Help on Photoelectric: Photoelectric:

PESewardite = 30.83 barns/electron
U=PESewardite x relectron= 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: 41.10.6.2 (41)Anhydrous Phosphates, etc. Containing Hydroxyl or Halogen
  (41.10)where (A++ B++)3 (XO4)2 Zq
  (41.10.6)Dana Group
 
41.10.6.1 Carminite PbFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m
 
41.10.6.2 Sewardite ! CaFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m
Help on Strunz Class: Strunz Class: VII/B.28-35 VII - Phosphates, Arsenates and Vanadates
  VII/B - Waterfree phosphates with unfamiliar anions F, Cl, O, OH. cations of medium and big size: Mg, Cu, Zn, and Ca, Na, K, Ba, Pb
  VII/B.28 - Carminite series
 
VII/B.28-10 Bertossaite Li2CaAl4(PO4)4(OH)4 Imaa,Iaa2 Ortho
 
VII/B.28-20 Palermoite (Sr,Ca)(Li,Na)2Al4(PO4)4(OH)4 I mmm 2/m 2/m 2/m
 
VII/B.28-30 Attakolite (Ca,Sr)Mn(Al,Fe)4[(Si,P)O4]H(PO4)3(OH)4 C 2/m 2/m
 
VII/B.28-35 Sewardite CaFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m
 
VII/B.28-40 Carminite PbFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m
 
VII/B.28-60 Leningradite PbCu3(VO4)Cl2 I bam 2/m 2/m 2/m
 
VII/B.28-70 Namibite CuBi2(VO4)O2 C 2/m,Cm,C 2 Mono
 
VII/B.28-80 Paganoite! (Ni,Co)BiAsO5 P1 1
 

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 -Google Images 4 -Google Scholar 5 -MinDAT 6 -MinMax(Deutsch) 7 -MinMax(English) 8 -Mineralienatlas (Deutsch) 9 -QUT Mineral Atlas

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Sewardite

CaFe+++2(AsO4)2(OH)2
Dana No: 41.10.6.2 Strunz No: VII/B.28-35
Locality:

 

Notes:

 
 
   
 
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