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Johnwalkite

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About JohnwalkiteHide

Formula:
K(Mn2+,Fe2+,Fe3+)2(Nb5+,Ta5+)(PO4)2O2 · 2(H2O,OH)
Hardness:
4
Crystal System:
Orthorhombic
Name:
Named for Richard JOHNson (1936-1998) and Frank WALKup (1943-1993), mineral preparators, National Museum of Natural History, Washington DC, USA.
The Mn analogue of olmsteadite.


Classification of JohnwalkiteHide

Approved
Approval Year:
1985
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
42.7.11.2

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

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

Physical Properties of JohnwalkiteHide

Hardness:

Optical Data of JohnwalkiteHide

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

Formula:
K(Mn2+,Fe2+,Fe3+)2(Nb5+,Ta5+)(PO4)2O2 · 2(H2O,OH)
IMA Formula:
K(Mn2+,Fe3+)2(Nb,Ta)O2(PO4)2 · 2(H2O,OH)

Crystallography of JohnwalkiteHide

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

Type Occurrence of JohnwalkiteHide

Synonyms of JohnwalkiteHide

Other Language Names for JohnwalkiteHide

Related Minerals - Nickel-Strunz GroupingHide

8.DJ.05OlmsteaditeKFe2+2(Nb5+,Ta5+)(PO4)2O2 · 2H2OOrth.
8.DJ.10GatumbaiteCaAl2(PO4)2(OH)2 · H2OMon. 2/m : P2/m
8.DJ.15CamgasiteCaMg(AsO4)(OH) · 5H2OMon. 2/m : P21/m
8.DJ.20Phosphofibrite(H2O,K)3.5Fe8(PO4)6(OH)7 · 5H2OMon. 2/m
8.DJ.20Meurigite-KKFe3+8(PO4)6(OH)7 · 6.5H2OMon. 2/m : B2/b
8.DJ.20Meurigite-NaNaFe3+8(PO4)6(OH)7 · 6.5H2OMon. 2/m : B2/b
8.DJ.25JungiteCa2Zn4Fe3+8(PO4)9(OH)9 · 16H2OOrth.
8.DJ.30WycheproofiteNaAlZr(PO4)2(OH) · H2OTric.
8.DJ.35ErcititeNa2Mn3+2(PO4)2(OH)2 · 4H2OMon.
8.DJ.40MrázekiteBi2Cu3(PO4)2O2(OH)2 · H2OMon. 2/m
8.DJ.45AttikaiteCa3Cu2Al2(AsO4)4(OH)4 · 2H2OOrth. mmm (2/m 2/m 2/m) : Pban

Related Minerals - Dana Grouping (8th Ed.)Hide

42.7.11.1OlmsteaditeKFe2+2(Nb5+,Ta5+)(PO4)2O2 · 2H2OOrth.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

22.5.1VauquelinitePb2Cu(CrO4)(PO4)(OH)Mon. 2/m
22.5.2EmbreyitePb5(CrO4)2(PO4)2 · H2OMon.
22.5.3CassedanneitePb5(CrO4)2(VO4)2 · H2OMon.
22.5.4FornacitePb2Cu(CrO4)(AsO4)(OH)Mon. 2/m : P21/b
22.5.5MolybdofornacitePb2Cu(MoO4,CrO4)(AsO4,PO4)(OH)Mon.
22.5.6Mendozavilite-NaFe[Na2(H2O)15Fe3+(H2O)6][Mo8P2Fe3+3O35(OH)2]Mon. 2/m : B2/m
22.5.7ParamendozaviliteNaAl4Fe7(PO4)5(PMo12O40)(OH)16 · 56H2OMon.
22.5.8Betpakdalite-CaCa[Ca2(H2O)17Ca(H2O)6][Mo6+8As5+2Fe3+3O36(OH)]Mon. 2/m : B2/m
22.5.9Betpakdalite-NaCa[Na2(H2O)17Ca(H2O)6][Mo6+8As5+2Fe3+3O34(OH)3]Mon. 2/m : B2/m
22.5.10Obradovicite-KCu[K2(H2O)17Cu(H2O)6][Mo8As2Fe3+3O34(OH)3]Orth. mmm (2/m 2/m 2/m) : Pmna
22.5.11Melkovite[Ca2(H2O)15Ca(H2O)6][Mo8P2Fe3+3O36(OH)]Mon. 2/m : B2/m
22.5.12RankachiteCa0.5(V4+,V5+)(W6+,Fe3+)2O8(OH) · 2H2OMon. 2/m : P21/m
22.5.13OlmsteaditeKFe2+2(Nb5+,Ta5+)(PO4)2O2 · 2H2OOrth.

Other InformationHide

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 JohnwalkiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
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 JohnwalkiteHide

Localities for JohnwalkiteHide

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.
USA (TL)
 
  • South Dakota
    • Pennington Co.
      • Keystone District
        • Keystone
NJMM (1986), 115; HB4 (2000)
Mineral and/or Locality  
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