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Selwynite

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Wycheproof granite quarry, Wycheproof, Victoria, Australia
© Knut Eldjarn

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Formula:
NaK(Be,Al)Zr
 
2
(PO
 
4
)
 
4
 · 2H
 
2
O
System:TetragonalColour:Deep purplish blue
Lustre:VitreousHardness:4
Member of:Gainesite Group
Name:The name honours Alfred Richard Cecil Selwyn (1824-1902), British born geologist, founding Director of the Geological Survey of Victoria, Australia (1860-1869), and the second Director of the Geological Survey of Canada (1869-1895).


Gainesite Group

Classification of Selwynite

IMA status:Approved
Strunz 8th edition ID:7/C.02-25
Nickel-Strunz 10th (pending) edition ID:8.CA.20

8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
A : With small and large/medium cations
Dana 8th edition ID:40.5.4.3

40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
5 : AXO4·xH2O
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Type Occurrence of Selwynite

Type Locality:Wycheproof granite quarry, Wycheproof, Victoria, Australia
Year of Discovery:1995

Physical Properties of Selwynite

Lustre:Vitreous
Diaphaneity (Transparency):Transparent, Translucent
Colour:Deep purplish blue
Streak:Lavender, pale
Hardness (Mohs):4

Crystallography of Selwynite

Crystal System:Tetragonal
Cell Parameters:a = 6.57Å, c = 17.14Å
Ratio:a:c = 1 : 2.609
Unit Cell Volume:V 739.85 ų (Calculated from Unit Cell)

Optical Data of Selwynite

Type:Uniaxial (+)
RI values: nω = 1.624 nε = 1.636
Maximum Birefringence:δ = 0.012

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Moderate

Chemical Properties of Selwynite

Formula:
NaK(Be,Al)Zr
 
2
(PO
 
4
)
 
4
 · 2H
 
2
O
Essential elements:Be, H, K, Na, O, P, Zr
All elements listed in formula:Al, Be, H, K, Na, O, P, Zr
Common Impurities:Rb,Ca,Sr,Ba,Mg,Mn,Fe,Cs,Ce,Hf,P,Si,F

Relationship of Selwynite to other Species

Member of:Gainesite Group
Other Members of Group:

- +
Gainesite
Na(Na,K)(Be,Li)Zr
 
2
(PO
 
4
)
 
4
 · 1.5-2H
 
2
O
Mccrillisite
NaCs(Be,Li)Zr
 
2
(PO
 
4
)
 
4
 · 1-2H
 
2
O
Related Minerals - Nickel-Strunz Grouping):

- +
8.CA.05Fransoletite
Ca
 
3
Be
 
2
(PO
 
4
)
 
2
(HPO
 
4
)
 
2
 · 4H
 
2
O
8.CA.05Parafransoletite
Ca
 
3
Be
 
2
(PO
 
4
)
 
2
(HPO
 
4
)
 
2
 · 4H
 
2
O
8.CA.10Ehrleite
Ca
 
4
Be
 
3
Zn
 
2
(PO
 
4
)
 
6
 · 9H
 
2
O
8.CA.15Faheyite
(Mn,Mg,Na)Be
 
2
Fe
 
2
(PO
 
4
)
 
4
 · 6H
 
2
O
8.CA.20Gainesite
Na(Na,K)(Be,Li)Zr
 
2
(PO
 
4
)
 
4
 · 1.5-2H
 
2
O
8.CA.20Mccrillisite
NaCs(Be,Li)Zr
 
2
(PO
 
4
)
 
4
 · 1-2H
 
2
O
8.CA.25Pahasapaite
Li
 
8
(Ca,Li,K)
 
10.5
Be
 
24
(PO
 
4
)
 
24
 · 38H
 
2
O
8.CA.30Hopeite
Zn
 
3
(PO
 
4
)
 
2
 · 4H
 
2
O
8.CA.30Arsenohopeite
Zn
 
3
(AsO
 
4
)
 
2
 · 4H
 
2
O
8.CA.35Warikahnite
Zn
 
3
(AsO
 
4
)
 
2
 · 2H
 
2
O
8.CA.40Phosphophyllite
Zn
 
2
Fe(PO
 
4
)
 
2
 · 4H
 
2
O
8.CA.45Parascholzite
CaZn
 
2
(PO
 
4
)
 
2
 · 2H
 
2
O
8.CA.45Scholzite
CaZn
 
2
(PO
 
4
)
 
2
 · 2H
 
2
O
8.CA.50Keyite
Cu
2+
3
Zn
 
4
Cd
 
2
(AsO
 
4
)
 
6
 · 2H
 
2
O
8.CA.55Pushcharovskite
K
 
0.6
Cu
 
18
(AsO
 
4
)(HAsO
 
4
)
 
10
(H
 
2
AsO
 
4
)
 
4
(OH)
 
9.6
·18.6H
 
2
O
8.CA.60Prosperite
CaZn
 
2
(AsO
 
4
)(HAsO
 
4
)(OH)
8.CA.65Gengenbachite
KFe
3+
3
(HPO
 
4
)
 
4
(H
 
2
PO
 
4
)
 
2
 · 6H
 
2
O
8.CA.70Parahopeite
Zn
 
3
(PO
 
4
)
 
2
 · 4H
 
2
O

Other Names for Selwynite

Synonyms:
IMA1993-037Potassian Gainesite
Other Languages:
German:Selwynit
Spanish:Selwynita

Other Information

Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Selwynite

Reference List:

- +
Birch, W.D. and D.A.Henry (1993), Phosphate Minerals of Victoria: 39.

Birch, W. D., Pring, A. & Foord, E. E. (1995): Selwynite, NaK(Be,Al)Zr2(PO4)4.2H2O, a new gainesite-like mineral from Wycheproof, Victoria, Australia. Canadian Mineralogist: 33: 55-58.

Mineralogical Record: 27: 120.


Internet Links for Selwynite

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Selwynite details from Handbook of Mineralogy (PDF)
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    • Localities for Selwynite

    The 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.
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    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    Australia
     
    • Victoria
    		Ulrich (1870). Contributions to the mineralogy of Victoria
    No reference listed
      • Wycheproof
    		CM 1995, 55-8
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