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Juansilvaite

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About JuansilvaiteHide

Formula:
Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2·4H2O
Colour:
Bright pink (crystals), dull pale pink (opaque aggregates)
Lustre:
Vitreous
Hardness:
Specific Gravity:
3.01
Crystal System:
Monoclinic
Name:
Honours Juan Silva Aguirre (1939-2012). Mr. Silva was a prominent Chilean mining engineer and among Chile’s most successful mining entrepreneurs. He was responsible for the development and operation of several important mines and a myriad of smaller ones in the Copiapo, Tierra Amarilla and Vallenar areas of the Atacama Region.
New structure type. The only Na-Al-As-S mineral (unique combination).

The associated minerals include mahnertite-like phase.

The structure is based on layers built of alternating corner-connected Al-O octahedra and acid-arsenate tetrahedra. There are two locations of the Na atoms: (1) at the layers periphery and (2) in cavities in the layers. The interlayer space also hosts sulphate tetrahedra and water.


Classification of JuansilvaiteHide

Approved
Approval Year:
2015
First Published:
2017

Physical Properties of JuansilvaiteHide

Vitreous
Transparency:
Transparent
Colour:
Bright pink (crystals), dull pale pink (opaque aggregates)
Streak:
white
Hardness:
2½ on Mohs scale
Comment:
ca. 2.5
Tenacity:
Brittle
Cleavage:
Very Good
{001}
Density:
3.01(2) g/cm3 (Measured)    3.005 g/cm3 (Calculated)

Optical Data of JuansilvaiteHide

Type:
Biaxial (+)
RI values:
nα = 1.575(1) nβ = 1.597(1) nγ = 1.623(1)
2V:
Measured: 86° (1), Calculated: 86.5°
Max Birefringence:
δ = 0.048
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
slight (r < v)
Comments:
Shades of pale pink (X > Y ≈ Z)
Comments:
2V = 86o; orientation: X = b; Z ^ c = 27o in the obtuse angle β

Chemical Properties of JuansilvaiteHide

Formula:
Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2·4H2O
IMA Formula:
Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2 · 4H2O

Crystallography of JuansilvaiteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Setting:
C2/c
Cell Parameters:
a = 18.1775(13) Å, b = 8.6285(5) Å, c = 18.5138(13) Å
β = 90.389(6)°
Ratio:
a:b:c = 2.107 : 1 : 2.146
Unit Cell V:
2903.7 ų
Z:
4
Morphology:
Crystals are flattened on {001} and elongated on [100]; observed forms include: {001}, {111} and {201}

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
9.25(100)
7.20(34)
4.545(34)
3.988(43)
3.363(42)
3.145(66)
2.960(68)
2.804(33)

Type Occurrence of JuansilvaiteHide

General Appearance of Type Material:
Blades, up to ca. 0.5 mm in length, in tightly intergrown radial aggregates; as opaque rounded aggregates
Place of Conservation of Type Material:
Cotype material is deposited in the collections of the Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles,CA 90007, USA, catalogue numbers 65605,65606, 65607 and 65608
Geological Setting of Type Material:
Secondary alteration mineral
Associated Minerals at Type Locality:
Reference:
Kampf, A.R., Nash, B.P., Dini, M., Molina Donoso, A.A. (2017): Juansilvaite, Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2·4H2O, a new arsenate-sulfate from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine: 81: 619–628.

Synonyms of JuansilvaiteHide

Other InformationHide

Notes:
Slowly soluble in dilute HCl at RT
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for JuansilvaiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Kampf, A.R., Nash, B., Dini, M. and Molina Donoso, A.A. (2015) Juansilvaite, IMA 2015-080. CNMNC Newsletter No. 28, December 2015, page 1863; Mineralogical Magazine: 79: 1859–1864.
Kampf, A.R., Nash, B.P., Dini, M., Molina Donoso, A.A. (2016): Juansilvaite, Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2·4H2O, a new arsenate-sulfate from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine: 81: 619–628.

Internet Links for JuansilvaiteHide

Localities for JuansilvaiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Chile (TL)
 
  • Tarapacá Region
    • Iquique Province
      • Salar Grande
Kampf, A.R., Nash, B., Dini, M. and Molina Donoso, A.A. (2015) Juansilvaite, IMA 2015-080. CNMNC Newsletter No. 28, December 2015, page 1863; Mineralogical Magazine, 79, 1859–1864; Kampf, A.R., Nash, B.P., Dini, M., Molina Donoso, A.A. (2017): Juansilvaite, Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2·4H2O, a new arsenate-sulfate from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine: 81: 619–628.
Mineral and/or Locality  
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