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Pyrochlore

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Orberg Quarry, Orberg Mt. - Badberg Mt. area, Schelingen, Kaiserstuhl, Baden-Württemberg, Germany

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Formula:
(Ca,Na)
 
2
Nb
 
2
O
 
6
(OH,F)
System:IsometricColour:Brown, yellow-brown, ...
Hardness:5 - 5½
Name:From the Greek πΰρ, fire, and χλωρός, green in allusion to the fact that the mineral usually turns green on ignition.
Isostructural with:Roméite


Pyrochlore Group. Pyrochlore Subgroup. Microlite-Pyrochlore Series. The niobium analogue of Microlite. The crystal structure is closely related to that of Pittongite.

Classification of Pyrochlore

IMA status:Approved
Strunz 8th edition ID:4/C.17-10
Nickel-Strunz 10th (pending) edition ID:4.DH.15

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
H : With large (+- medium-sized) cations; sheets of edge-sharing octahedra
Dana 8th edition ID:8.2.1.1

8 : MULTIPLE OXIDES CONTAINING NIOBIUM,TANTALUM OR TITANIUM
2 : A2B2O6(O,OH,F)
Hey's CIM Ref.:18.2.8

18 : Niobates and Tantalates
2 : Niobates and tantalates containing rare earths but not U
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Type Occurrence of Pyrochlore

Type Locality:Stavern (Fredriksvärn), Larvik, Vestfold, Norway
Year of Discovery:1826

Occurrences of Pyrochlore

Geological Setting:Pegmatites in nepheline syenites, granitic pegmatites and greisens, carbonatites.

Physical Properties of Pyrochlore

Lustre:Vitreous, Resinous
Diaphaneity (Transparency):Transparent, Translucent on thin edges
Colour:Brown, yellow-brown, reddish brown, orange, black
Streak:Light brown, yellow-brown
Hardness (Mohs):5 - 5½
Hardness (Vickers):VHN100=542 - 665 kg/mm2
Tenacity:Brittle
Cleavage:Distinct/Good
Octahedral {111} (may be a parting), sometimes distinct but usually not distinguishable.
Fracture:Irregular/Uneven, Splintery, Sub-Conchoidal
Density (measured):4.45 - 4.9 g/cm3
Density (calculated):4.33 g/cm3
Comment:Density increases with uranium content.

Crystallography of Pyrochlore

Crystal System:Isometric
Class (H-M):m3m (4/m 3 2/m) - Hexoctahedral
Space Group:Fd3m (F41/d 3 2/m)
Cell Parameters:a = 10.41(6) Å
Unit Cell Volume:V 1,128.11 ų (Calculated from Unit Cell)
Z:8
Morphology:Crystals octahedral, often with subordinate {011}, {113} or {001}. Irregular masses and embedded grains.
Twinning:Twin plane {111} (spinel law twins), rare.
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data: Peaks:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Chemical Properties of Pyrochlore

Formula:
(Ca,Na)
 
2
Nb
 
2
O
 
6
(OH,F)
Essential elements:Ca, H, Nb, O
All elements listed in formula:Ca, F, H, Na, Nb, O
Common Impurities:Fe,Mg,Mn,U,Ta,Ti

Relationship of Pyrochlore to other Species

Series:Forms a series with Microlite (see here)
Related to:
  • Pyrochlore Group
  • Pyrochlore Subgroup
    • Related Minerals - Nickel-Strunz Grouping):
    4.DH.05Brannerite
    (U
    4+
     
    		,Ca)(Ti,Fe
    3+
     
    		)
     
    2
    		O
     
    6
    4.DH.05Orthobrannerite
    UTi
     
    4
    		O
     
    12
    		(OH)
     
    2
    4.DH.05Thorutite
    (Th,U,Ca)Ti
     
    2
    		(O,OH)
     
    6
    4.DH.10Kassite
    CaTi
     
    2
    		O
     
    4
    		(OH)
     
    2
    4.DH.10Lucasite-(Ce)
    CeTi
     
    2
    		(O,OH)
     
    6
    4.DH.15Alumotungstite
    (W,Al)(O,OH)
     
    3
    4.DH.15Bariomicrolite
    Ba(Ta,Nb)
     
    2
    		(O,OH)
     
    7
    4.DH.15Bariopyrochlore
    (Ba,Sr)
     
    2
    		(Nb,Ti)
     
    2
    		(O,OH)
     
    7
    4.DH.15Betafite
    (Ca,U)
     
    2
    		(Ti,Nb)
     
    2
    		O
     
    6
    		(OH)
    4.DH.15Bismutomicrolite
    (Bi,Ca)(Ta,Nb)
     
    2
    		O
     
    6
    		(OH)
    4.DH.15Calciobetafite
    (Ca,RE,Th,U)
     
    2
    		(Nb,Ta,Ti)
     
    2
    		O
     
    7
    4.DH.15Ceriopyrochlore-(Ce)
    (Ce,Ca,Y)
     
    2
    		(Nb,Ta)
     
    2
    		O
     
    6
    		(OH,F)
    4.DH.15Cesstibtantite
    (Cs,Na)SbTa
     
    4
    		O
     
    12
    4.DH.15Ferritungstite
    (W,Fe
    3+
     
    		)(O,OH)
     
    3
    4.DH.15Jixianite
    Pb(W,Fe
    3+
     
    		)
     
    2
    		(O,OH)
     
    7
    4.DH.15Kalipyrochlore
    (K,Sr)
     
    2-x
    		Nb
     
    2
    		O
     
    6
    		(O,OH)·nH
     
    2
    		O
    4.DH.15Microlite
    (Ca,Na)
     
    2
    		Ta
     
    2
    		O
     
    6
    		(O,OH,F)
    4.DH.15Natrobistantite
    (Na,Cs)Bi(Ta,Nb,Sb)
     
    4
    		O
     
    12
    4.DH.15Plumbopyrochlore
    (Pb,Y,U,Ca)
     
    2-x
    		Nb
     
    2
    		O
     
    6
    		(OH)
    4.DH.15Plumbomicrolite
    (Pb,Ca,U)
     
    2
    		Ta
     
    2
    		O
     
    6
    		(OH)
    4.DH.15Plumbobetafite
    (Pb,U,Ca)(Ti,Nb)
     
    2
    		O
     
    6
    		(OH,F)
    4.DH.15Stibiomicrolite
    (Sb,Ca,Na)
     
    2
    		(Ta,Nb)
     
    2
    		O
     
    7
    4.DH.15Strontiopyrochlore
    (Sr,Ce,Ca)
     
    0.66
    		(Nb,Fe)
     
    2
    		(O,OH)
     
    7
    4.DH.15Stannomicrolite
    (Sn,Fe,Mn)
     
    2
    		(Ta,Nb,Sn)
     
    2
    		(O,OH)
     
    7
    4.DH.15Stibiobetafite
    (Sb,Ca)
     
    2
    		(Ti,Nb,Ta)
     
    2
    		(O,OH)
     
    7
    4.DH.15Uranmicrolite
    (U,Ca,Ce)
     
    2
    		(Ta,Nb)
     
    2
    		O
     
    6
    		(OH,F)
    4.DH.15Uranpyrochlore
    (U,Ca,Ce)
     
    2
    		(Nb,Ta)
     
    2
    		O
     
    6
    		(OH,F)
    4.DH.15Yttrobetafite-(Y)
    (Y,U,Ce)
     
    2
    		(Ti,Nb,Ta)
     
    2
    		O
     
    6
    		OH
    4.DH.15Yttropyrochlore-(Y)
    (Y,Na,Ca,U)
     
    1-2
    		(Nb,Ta,Ti)
     
    2
    		(O,OH)
     
    7
    4.DH.15Fluornatromicrolite
    (Na,Ca,Bi)
     
    2
    		Ta
     
    2
    		O
     
    6
    		F
    4.DH.15Bismutopyrochlore
    (Bi,U,Ca,Pb)
     
    1+x
    		(Nb,Ta)
     
    2
    		O
     
    6
    		(OH)·nH
     
    2
    		O
    4.DH.15Thorian Pyrochlore
    4.DH.15Elsmoreite
    WO
     
    3
    		·0.5H
     
    2
    		O
    4.DH.20Bismutostibiconite
    Bi(Sb
    5+
     
    		,Fe
    3+
     
    		)
     
    2
    		O
     
    7
    4.DH.20Bindheimite
    Pb
     
    2
    		Sb
     
    2
    		O
     
    6
    		(O,OH)
    4.DH.20Monimolite
    (Pb,Ca,Fe)
     
    3
    		Sb
     
    2
    		O
     
    7
    4.DH.20Partzite
    Cu
     
    2
    		Sb
     
    2
    		(O,OH)
     
    7
    4.DH.20Roméite
    (Ca,Fe,Mn,Na)
     
    2
    		(Sb,Ti)
     
    2
    		O
     
    6
    		(O,OH,F)
    4.DH.20Stetefeldtite
    Ag
     
    2
    		Sb
     
    2
    		(O,OH)
     
    7
    4.DH.20Stibiconite
    SbSb
     
    2
    		O
     
    6
    		(OH)
    4.DH.25Rosiaite
    PbSb
    5+
    2
    		O
     
    6
    4.DH.30Zirconolite
    CaZrTi
     
    2
    		O
     
    7
    4.DH.35Liandratite
    U(Nb,Ta)
     
    2
    		O
     
    8
    4.DH.35Petscheckite
    UFe(Nb,Ta)
     
    2
    		O
     
    8
    4.DH.40Ingersonite
    Ca
     
    3
    		MnSb
     
    4
    		O
     
    14
    4.DH.45Pittongite
    Na
     
    0.22
    		(W,Fe
    3+
     
    		)(O,OH)
     
    3
    		 · 0.44H
     
    2
    		O
    Related Minerals - Hey's Index Grouping:
    18.2.1Fergusonite-(Y)
    YNbO
     
    4
    18.2.2β-Fergusonite-(Y)
    YNbO
     
    4
    18.2.3Fergusonite-(Ce)
    (Ce,La,Nd)NbO
     
    4
    18.2.4β-Fergusonite-(Ce)
    (Ce,La,Nd)NbO
     
    4
    18.2.5Fergusonite-(Nd)
    (Nd,Ce)(Nb,Ti)O
     
    4
    18.2.6β-Fergusonite-(Nd)
    (Nd,Ce)NbO
     
    4
    18.2.7Formanite-(Y)
    YTaO
     
    4
    18.2.9Ceriopyrochlore-(Ce)
    (Ce,Ca,Y)
     
    2
    		(Nb,Ta)
     
    2
    		O
     
    6
    		(OH,F)
    18.2.10Strontiopyrochlore
    (Sr,Ce,Ca)
     
    0.66
    		(Nb,Fe)
     
    2
    		(O,OH)
     
    7
    18.2.11Loparite-(Ce)
    (Na,Ce,Ca,Sr,Th)(Ti,Nb,Fe)O
     
    3
    18.2.12Fersmite
    (Ca,Ce,Na)(Nb,Ta,Ti)
     
    2
    		(O,OH,F)
     
    6
    18.2.13Aeschynite-(Ce)
    (Ce,Ca,Fe,Th)(Ti,Nb)
     
    2
    		(O,OH)
     
    6
    18.2.14Aeschynite-(Nd)
    (Nd,Ce,Ca)(Ti,Nb)
     
    2
    		(O,OH)
     
    6
    18.2.15Aeschynite-(Y)
    (Y,Ca,Fe,Th)(Ti,Nb)
     
    2
    		(O,OH)
     
    6
    18.2.16Nioboaeschynite-(Ce)
    (Ce,Ca,Th)(Nb,Ti)
     
    2
    		(O,OH)
     
    6
    18.2.17Niobo-aeschynite-(Nd)
    (Nd,Ce)(Nb,Ti)
     
    2
    		(O,OH)
     
    6
    18.2.18Tantalaeschynite-(Y)
    (Y,Ce,Ca)(Ta,Ti,Nb)
     
    2
    		O
     
    6
    18.2.19Vigezzite
    (Ca,Ce)(Nb,Ti)
     
    2
    		O
     
    6
    18.2.20Murataite-(Y)
    (Na,Y)
     
    4
    		(Zn,Fe)
     
    3
    		(Ti,Nb)
     
    6
    		O
     
    18
    		(F,OH)
     
    4

    Other Names for Pyrochlore

    Synonyms:
    Azor-PhyrriteAzor-pyrrhiteColumbomicroliteEndeioliteFluochlor
    HydrochlorKoppiteNiobpyrochlorPyrochlor
    German names:
    Azor-PhyrritAzor-pyrrhitColumbomicrolitColumbomikrolithKoppit
    Pyrrhit
    Russian names:
    Пирохлор
    Spanish names:
    ColumbomicrolitaKoppita
    Varieties:
    Thorian PyrochloreZirconian Pyrochlore

    Other Information

    Health Warning:May be radioactive.

    References for Pyrochlore

    Reference List:Wöhler (1826), Ann. Pys.: 7: 417.

    Rose (1840), Ann. Phys.: 48: 562 (as Pyrrhit).

    Knop (1875), Jb. Min.: 67.

    Allen (1877), American Journal of Science: 14: 128 (as Hatchettolite).

    Smith (1877), American Journal of Science: 13: 365 (as Hatchettolite).

    Hubbard (1886), Verh. natur-hist. Ver. preuss. Rheinland, Sitzber.: 43: 217 (as Azor-pyrrhit).

    Holmqist (1896), Geological Institute Upsala, Bulletin: 3: 181 (as uranpyrochlore).

    Flink (1898), Meddelelser om Grønland: 14: 234 (as chalcolamprite).

    Flink (1901), Meddelelser om Grønland: 24: 166 (as Endeiolite).

    Gaertner (1930), Jb. Min., Beil.-Bd.: 61: 1.

    Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 748-756.

    Hogarth, D.D. (1961) A study of pyrochlore and betafite. Canadian Mineralogist: 6: 610-633.

    American Mineralogist (1977): 62: 403-410.

    Hogarth, D.D. (1989) Pyrochlore, apatite and amphibole: distinctive minerals in carbonatite. In K. Bell, Ed., Carbonatites: Genesis and Evolution: 105-148. Unwin Hyman Ltd., London.

    Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (1997) Handbook of Mineralogy, Volume III. Halides, Hydroxides, Oxides. Mineral Data Publishing, Tucson, AZ, 628pp.: 457.

    Bonazzi, P., Bindi, L., Zoppi, M., Capitani, G.C., and Olmi, F. (2006) Single-crystal diffraction and transmission electron microscopy studies of "silicified" pyrochlore from Narssârssuk, Julianehaab district, Greenland. American Mineralogist: 91: 794-801.

    Birch, W.D., Grey, I.E., Mills, S.J., Bougerol, C., Pring, A., Ansermet, S. (2007): Pittongite, a new secondary tungstate from Pittong, Victoria, Australia. Canadian Mineralogist, 45, 857-864.

    Internet Links for Pyrochlore

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Pyrochlore in the Natural History Museum (London) online catalogue
  • Pyrochlore details from Handbook of Mineralogy (PDF)
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