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Johnwalkite

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Champion Mine, Keystone, Keystone District, Pennington Co., South Dakota, USA
© 2008, JGW




Formula:
K(Mn
2+
 
,Fe
2+
 
,Fe
3+
 
)
 
2
(Nb
5+
 
,Ta
5+
 
)(PO
 
4
)
 
2
O
 
2
 · 2(H
 
2
O,OH)
System:OrthorhombicHardness:4


The Mn analogue of olmsteadite.

Classification of Johnwalkite

IMA status:Approved 1985
Strunz 8th edition ID:7/D.39-20
Nickel-Strunz 10th (pending) edition ID:8.DJ.05

8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
J : With large and medium-sized cations, (OH, etc.):RO4 = 1:1
Dana 8th edition ID:42.7.11.2

42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
7 : (AB)2(XO4)Zq·xH2O
Hey's CIM Ref.:22.5.14

22 : Phosphates, Arsenates or Vanadates with other Anions
5 : Phosphates, arsenates or vanadates with chromate, molybdate, niobate or tantalate
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Type Occurrence of Johnwalkite

Type Locality:Champion Mine, Keystone, Keystone District, Pennington Co., South Dakota, USA
Year of Discovery:1986

Physical Properties of Johnwalkite

Hardness (Mohs):4

Crystallography of Johnwalkite

Crystal System:Orthorhombic
Cell Parameters:a = 7.51Å, b = 10.02Å, c = 6.5Å
Ratio:a:b:c = 0.75 : 1 : 0.649
Unit Cell Volume:V 489.13 ų (Calculated from Unit Cell)

Optical Data of Johnwalkite

Type:Biaxial (+)
RI values: nα = 1.748 nβ = 1.763 nγ = 1.840
2V:Measured: 53° , Calculated: 50°
Maximum Birefringence:δ = 0.092

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:High
Dispersion:r > v strong

Chemical Properties of Johnwalkite

Formula:
K(Mn
2+
 
,Fe
2+
 
,Fe
3+
 
)
 
2
(Nb
5+
 
,Ta
5+
 
)(PO
 
4
)
 
2
O
 
2
 · 2(H
 
2
O,OH)
Essential elements:H, K, Mn, Nb, O, P
All elements listed in formula:Fe, H, K, Mn, Nb, O, P, Ta

Relationship of Johnwalkite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
8.DJ.05Olmsteadite
KFe
2+
2
(Nb
5+
 
,Ta
5+
 
)(PO
 
4
)
 
2
O
 
2
 · 2H
 
2
O
8.DJ.10Gatumbaite
CaAl
 
2
(PO
 
4
)
 
2
(OH)
 
2
 · H
 
2
O
8.DJ.15Camgasite
CaMg(AsO
 
4
)(OH) · 5H
 
2
O
8.DJ.20Phosphofibrite
K
 
<0.5
(Fe
3+
 
,Cu)
 
8
(PO
 
4
)
 
6
(OH)
 
7
 · 7H
 
2
O
8.DJ.20Meurigite-K
KFe
3+
8
(PO
 
4
)
 
6
(OH)
 
7
 · 6.5H
 
2
O
8.DJ.20Meurigite-Na
NaFe
3+
8
(PO
 
4
)
 
6
(OH)
 
7
 · 6.5H
 
2
O
8.DJ.25Jungite
Ca
 
2
Zn
 
4
Fe
3+
8
(PO
 
4
)
 
9
(OH)
 
9
 · 16H
 
2
O
8.DJ.30Wycheproofite
NaAlZr(PO
 
4
)
 
2
(OH) · H
 
2
O
8.DJ.35Ercitite
Na
 
2
Mn
3+
2
(PO
 
4
)
 
2
(OH)
 
2
 · 4H
 
2
O
8.DJ.40Mrázekite
Bi
 
2
Cu
 
3
(PO
 
4
)
 
2
O
 
2
(OH)
 
2
 · H
 
2
O
8.DJ.45Attikaite
Ca
 
3
Cu
 
2
Al
 
2
(AsO
 
4
)
 
4
(OH)
 
4
 · 2H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
22.5.1Vauquelinite
Pb
 
2
Cu(CrO
 
4
)(PO
 
4
)(OH)
22.5.2Embreyite
Pb
 
5
(CrO
 
4
)
 
2
(PO
 
4
)
 
2
 · H
 
2
O
22.5.3Cassedanneite
Pb
 
5
(CrO
 
4
)
 
2
(VO
 
4
)
 
2
 · H
 
2
O
22.5.4Fornacite
Pb
 
2
Cu(CrO
 
4
)(AsO
 
4
)(OH)
22.5.5Molybdofornacite
Pb
 
2
Cu(MoO
 
4
,CrO
 
4
)(AsO
 
4
,PO
 
4
)(OH)
22.5.6Mendozavilite
Na(Ca,Mg)
 
2
Fe
3+
6
(PMo
 
11
O
 
39
)(PO
 
4
)
 
2
(OH,Cl)
 
10
 · 33H
 
2
O
22.5.7Paramendozavilite
NaAl
 
4
Fe
3+
7
(PMo
 
12
O
 
40
)(PO
 
4
)
 
5
(OH)
 
16
 · 56H
 
2
O
22.5.8Betpakdalite
{Mg(H
 
2
O)
 
6
}Ca
 
2
(H
 
2
O)
 
13
[Mo
6+
8
As
5+
2
Fe
3+
3
O
 
36
(OH)](H
 
2
O)
 
4
22.5.9Natrobetpakdalite
(Na
 
2
,Ca)Fe
 
2
(As
 
2
Mo
 
6
O
 
28
) · 15H
 
2
O
22.5.10Obradovicite
H
 
4
(K,Na)CuFe
 
2
(MoO
 
4
)
 
5
(AsO
 
4
) · 12H
 
2
O
22.5.11Melkovite
CaFe
3+
2
Mo
 
5
(PO
 
4
)
 
2
O
 
10
(OH)
 
12
 · 8H
 
2
O
22.5.12Rankachite
Ca
 
0.5
(V
4+
 
,V
5+
 
)(W
6+
 
,Fe
3+
 
)
 
2
O
 
8
(OH) · 2H
 
2
O
22.5.13Olmsteadite
KFe
2+
2
(Nb
5+
 
,Ta
5+
 
)(PO
 
4
)
 
2
O
 
2
 · 2H
 
2
O

Other Names for Johnwalkite

Synonyms:
IMA1985-008
Other Languages:
German:Johnwalkit
Russian:Джонуолкит
Spanish:Johnwalkita

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 Johnwalkite

Reference List:

- +
Dunn, P. J.; Peacor, D. R.; Sturman, D. B.; Ramik, R. A.; Roberts, W. L.; Nelen, J. A. (1986): Johnwalkite, the manganese analog of olmsteadite, from South Dakota. Neues Jahrbuch für Mineralogie, Monatshefte 1986, 115-120.

American Mineralogist (1987): 72: 223.

Internet Links for Johnwalkite

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    • Localities for Johnwalkite

    Hide Locality List
    (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.
    USA
     
    • South Dakota
      • Pennington Co.
        • Keystone District
          • Keystone
    		NJMM (1986), 115; HB4 (2000)
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