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Sewardite Mineral Data
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General Sewardite Information
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 Chemical Formula: |
CaFe+++2(AsO4)2(OH)2 |
| Composition: |
Molecular Weight = 464.68 gm |
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Calcium 8.62 % Ca 12.07 % CaO |
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Zinc 1.41 % Zn 1.75 % ZnO |
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Iron 22.83 % Fe 32.65 % Fe2O3 |
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Arsenic 32.25 % As 49.46 % As2O5 |
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Hydrogen 0.46 % H 4.07 % H2O |
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Oxygen 34.43 % O |
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______ ______ |
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100.00 % 100.00 % = TOTAL OXIDE |
| Empirical Formula: |
CaFe3+1.9Zn0.1(AsO4)2(OH)1.9(H2O)0.1 |
| Environment: |
Intergrown with ferrilotharmeyerite and another unknown. (Ca-dominant analogue of carminite; structure) |
| IMA Status: |
Approved IMA 2002 (Dana # Added) |
| Locality: |
31st Level, Tsumeb mine, Tsumeb, Namibia. Link to MinDat.org Location Data. |
| Name Origin: |
Named for Terry Maxwell Seward (1940-) who collected the mineral. |
| Synonym: |
IMA2001-054 |
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Sewardite Image |
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Images:
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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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Images:
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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 |
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Sewardite Crystallography
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| Axial Ratios: |
a:b:c =2.2142:1:1.6318 |
| Cell Dimensions: |
a = 16.461, b = 7.434, c = 12.131, Z = 8; V = 1,484.48 Den(Calc)= 4.16 |
| Crystal System: |
Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: C ccm |
| 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), |
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Physical Properties of Sewardite
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| Cleavage: |
{100} Imperfect, {011} Imperfect |
| Color: |
Dark red, Lighter red orange. |
| Diaphaneity: |
Translucent |
| Fracture: |
Splintery - Thin, elongated fractures produced by intersecting good cleavages or partings (e.g. hornblende). |
| Habit: |
Aggregates - Made of numerous individual crystals or clusters. |
| Habit: |
Anhedral Grains - Granular minerals without the expression of crystal shapes |
| Habit: |
Platy - Sheet forms (e.g. micas). |
| Hardness: |
3.5 - Copper Penny |
| Luster: |
Vitreous (Glassy) |
| Streak: |
reddish brown |
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Optical Properties of Sewardite
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| Optical Data: |
NCalc= 1.94 - from Gladstone-Dale relationship (KC = 0.2249) where Ncalc=Dcalc*KC+1
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| RL Anisotrophism: |
None. |
| RL Bireflectance: |
Weak. |
| RL Color: |
Light bluish gray with bright pink to red internal reflections. |
| RL Pleochroism: |
None. |
| Reflectivity |
Standardized Intensity (100%) Reflection Spectra of Sewardite in Air
| λ |
R1 |
R2 |
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∑ R1(λ) |
∑ R2(λ) |
| 460 nm |
10.12 |
10.71 |
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| 540 nm |
9.53 |
10.07 |
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| 580 nm |
9.30 |
9.98 |
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| 640 nm |
8.99 |
9.66 |
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Calculated Relative Intensity Colors of Sewardite in Air
Relative
Intensity |
0% |
100% |
200% |
300% |
400% |
500% |
600% |
700% |
800% |
900% |
950% |
| R1 |
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| R2 |
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Calculated Properties of Sewardite
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| Electron Density: |
Bulk Density (Electron Density)=3.95 gm/cc
note: Specific Gravity of Sewardite =4.16 gm/cc.
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| Fermion Index: |
Fermion Index = 0.0057003424
Boson Index = 0.9942996576 |
| Photoelectric: |
PESewardite = 30.83 barns/electron
U=PESewardite x rElectron Density= 121.72 barns/cc.
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| Radioactivity: |
GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Sewardite is Not Radioactive |
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Sewardite Classification
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| Dana Class: |
41.10.06.02 (41)Anhydrous Phosphates, etc. Containing Hydroxyl or Halogen |
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(41.10)where (A++ B++)3 (XO4)2 Zq |
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(41.10.06)Carminite Group |
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41.10.06.01 Carminite PbFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m |
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41.10.06.02 Sewardite! CaFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m |
| Strunz Class: |
08.BH.30 08 - PHOSPHATES, ARSENATES, VANADATES |
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08.B - Phosphates, etc. with Additional Anions, without H2O |
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08.BH -With medium-sized and large cations, (OH,etc.):RO4 = 1:1 |
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08.BH.30 Carminite PbFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m |
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08.BH.30 Sewardite! CaFe2(AsO4)2(OH)2 C ccm 2/m 2/m 2/m |
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Other Sewardite Information
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| References: |
NAME( AmMin, v 88, p 1178) PHYS. PROP.(AmMin, v 88, p 1178) OPTIC PROP.(AmMin, v 88, p 1178) |
| 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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Sewardite
CaFe+++2(AsO4)2(OH)2
Dana No: 41.10.06.02 Strunz No: 08.BH.30
Locality:
Notes:
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