Afwillite (original) (raw)
A valid IMA mineral species - grandfathered
About AfwilliteHide
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Formula:
Ca3[SiO4][SiO2(OH)2] · 2H2O
Colour:
Colourless, white; rarely blue
Crystal System:
Monoclinic
Name:
Named in 1925 by John Parry and Frederick Eugene Wright in honor of Alpheus Fuller Williams [June 21, 1874 Oakland Alameda County California, USA - January 6, 1953 Cape Town, Western Cape, South Africa] of the De Beers Consolidated Mines of South Africa.
This page provides mineralogical data about Afwillite.
Unique IdentifiersHide
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Long-form identifier:
mindat:1:1:42:6
2a5adcc3-a29a-4403-8101-7da960705a4a
IMA Classification of AfwilliteHide
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Approved, 'Grandfathered' (first described prior to 1959)
Type description reference:
Classification of AfwilliteHide
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9.AG.75
9 : SILICATES (Germanates)
A : Nesosilicates
G : Nesosilicates with additional anions; cations in > [6] +- [6] coordination
52.4.7.1
52 : NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
4 : Insular SiO4 Groups and O, OH, F, and H2O with cations in [6] and/or >[6] coordination
14.5.11
14 : Silicates not Containing Aluminum
5 : Silicates of Ca
Mineral SymbolsHide
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As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference |
|---|---|---|
| Afw | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of AfwilliteHide
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Colour:
Colourless, white; rarely blue
Cleavage:
Perfect
Perfect on {101}, good on {100}
Density:
2.630 g/cm3 (Measured) 2.643(5) g/cm3 (Calculated)
Optical Data of AfwilliteHide
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RI values:
_n_α = 1.617 _n_β = 1.620 _n_γ = 1.634
δ = 0.017
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Optical Extinction:
Y = b; X ∧ c = 31.2°.
Chemistry of AfwilliteHide
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Mindat Formula:
Ca3[SiO4][SiO2(OH)2] · 2H2O
Common Impurities:
Al,Fe,Mg,F
Crystallography of AfwilliteHide
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Crystal System:
Monoclinic
Cell Parameters:
a = 16.278(1) Å, b = 5.6321(4) Å, c = 13.236(1) Å
β = 134.9°
Ratio:
a:b:c = 2.89 : 1 : 2.35
Unit Cell V:
859.55 ų (Calculated from Unit Cell)
Morphology:
Crystals are prismatic, tabular, radial fibrous spherulites, massive.
Known forms include {001}, {100}, {110}, {310}, {011}, {045}, {013}, {101}, {101}, {302}, {112}, {121}, {211}, {213}, {312}.
Crystal StructureHide
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X-Ray Powder DiffractionHide
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Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.83 Å | (100) |
| 6.61 Å | (90) |
| 3.18 Å | (90) |
| 2.73 Å | (90) |
| 3.28 Å | (70) |
| 2.15 Å | (70) |
| 2.34 Å | (60) |
Comments:
Dutoitspan mine, Kimberley, South Africa. Data from Switzer and Bailey (1953).
Geological EnvironmentHide
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Geological Setting:
Contact metamorphism of limestones.
Type Occurrence of AfwilliteHide
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General Appearance of Type Material:
Large crystals (11 x 4 x 1.5 cm) composed of sub-parallel individuals.
Place of Conservation of Type Material:
The Natural History Museum, London, England, number 1925,80 (cotype).
National Museum of Natural History, Washington, D.C., USA, number 95237 (type).
Geological Setting of Type Material:
In a large dolerite inclusion in kimberlite.
Associated Minerals at Type Locality:
Reference:
Parry, J., Wright, F.E. (1925) Afwillite, a new hydrous calcium silicate, from Dutoitspan mine, Kimberley, South Africa. Mineralogical Magazine: 20: 277-285.
Other Language Names for AfwilliteHide
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Common AssociatesHide
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Associated Minerals Based on Photo Data:
Related Minerals - Strunz-mindat GroupingHide
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Other InformationHide
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Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for AfwilliteHide
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References for AfwilliteHide
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Localities for AfwilliteHide
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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
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- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for references and 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 (e.g. from pseudomorphs).
All localities listed without proper references should be considered as questionable.