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Pyrochlore Group

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Formula:
A
 
2
Nb
 
2
(O,OH)
 
6
Z
A is Na, Ca, Sn2+, Sr, Pb2+, Sb3+, Y, U4+, H2O or ◻.

Z is OH, F, O, H2O or ◻
System:IsometricColour:Brown, yellow-brown, ...
Hardness:5 - 5½
Member of:Pyrochlore Supergroup
Name:From the Greek πΰρ, fire, and χλωρός, green in allusion to the fact that the mineral usually turns green on ignition.


The nomenclature was recently revised by Atencio et al. (2010) and Christy and Atencio (2013).

Classification of Pyrochlore Group

IMA status:Redefined Approved 2010
Strunz 8th edition ID:4/0.0-
Nickel-Strunz 10th (pending) edition ID:4.00.

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
0 :
0 :
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 Group

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

Occurrences of Pyrochlore Group

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

Physical Properties of Pyrochlore Group

Lustre:Vitreous, Resinous
Diaphaneity (Transparency):Transparent
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 Group

Crystal System:Isometric
Class (H-M):m3m (4/m 3 2/m) - Hexoctahedral
Space Group:Fd3m
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:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Chemical Properties of Pyrochlore Group

Formula:
A
 
2
Nb
 
2
(O,OH)
 
6
Z


A is Na, Ca, Sn2+, Sr, Pb2+, Sb3+, Y, U4+, H2O or ◻.

Z is OH, F, O, H2O or ◻
Simplified for copy/paste:A2Nb2(O,OH)6Z
Common Impurities:Fe,Mg,Mn,U,Ta,Ti

Relationship of Pyrochlore Group to other Species

Member of:Pyrochlore Supergroup
Other Members of Group:

- +
Group Members:
Fluorcalciopyrochlore 
(Ca,Na,□)
 
2
Nb
 
2
(O,OH)
 
6
(F,OH)
Fluorkenopyrochlore 
(□,Sr,Ce,Ca,Na)
 
2
(Nb,Ti)
 
2
O
 
6
F
Fluornatropyrochlore 
(Na,REE,Ca)
 
2
Nb
 
2
(O,OH)
 
6
F
Fluorplumbopyrochlore 
(Pb,Y,Th,U,Na,Ca)
 
2-x
(Nb,Ti)
 
2
O
 
6
F
Fluorstrontiopyrochlore 
(Sr,□)
 
2
Nb
 
2
(O,OH)
 
6
F
Hydropyrochlore 
(H
 
2
O,□)
 
2
Nb
 
2
(O,OH)
 
6
(H
 
2
O)
Hydroxycalciopyrochlore 
(Ca,Na,U,□)
 
2
(Nb,Ti)
 
2
O
 
6
(OH)
Hydroxymanganopyrochlore 
(Mn
2+
 
,Th,Na,Ca,REE)
 
2
(Nb,Ti)
 
2
O
 
6
(OH)
Hydroxyplumbopyrochlore 
(Pb,Ca)
 
2-x
(Nb,Ti,Ta)
 
2
O
 
6
(OH)
Kenoplumbopyrochlore 
(Pb,□)Nb
 
2
O
 
6
(□,O)
Oxycalciopyrochlore 
Ca
 
2
Nb
 
2
O
 
6
O
Oxynatropyrochlore 
(Na,Ca,U)
 
2
Nb
 
2
O
 
6
(O,OH)
Oxyplumbopyrochlore 
Pb
 
2
Nb
 
2
O
 
6
O
Oxyyttropyrochlore-(Y) 
(Y,◻)
 
2
Nb
 
2
O
 
6
O
Related Minerals - Nickel-Strunz Grouping):

- +
4.00.Microlite Group
4.00.Roméite Group
4.00.Písekite-(Y)
(Y,As,Ca,Fe,U)(Nb,Ti,Ta)O
 
4
4.00.UM2004-19-O:AlCeGdZr
(Gd,Ce)
 
4
Al
 
2
Zr
 
4
O
 
17
4.00.UM2004-21-O:CaFeGdZr
Ca
 
2
Gd
 
4
Fe
 
5
ZrO
 
15
4.00.UM2004-27-O:GdTi
Gd
 
2
Ti
 
4
O
 
11
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 (of Hogarth 1977)
18.2.10Strontiopyrochlore (of Hogarth 1977)
18.2.11Loparite-(Ce)
(Na,Ce,Ca,Sr,Th)(Ti,Nb,Fe)O
 
3
18.2.12Fersmite
(Ca,Y)(Nb,Ta,Ti)
 
2
(O,OH)
 
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
18.2.17Nioboaeschynite-(Nd)
(Nd,Ce,Ca,Th)(Nb,Ti,Fe,Ta)
 
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)
(Y,Na)
 
6
Zn(Zn,Fe
3+
 
)
 
4
(Ti,Nb,Na)
 
12
O
 
29
(O,F,OH)
 
10
F
 
4

Other Names for Pyrochlore Group

Synonyms:
Azor-PhyrriteAzor-pyrrhiteAzorpyrrhiteColumbomicrolite (of De Villiers)Endeiolite
FluochlorHydrochlorKoppiteNiobpyrochlorPyrochlor
Other Languages:
German:Azor-Phyrrit
Azor-pyrrhit
Columbomicrolit
Columbomikrolith
Koppit
Pyrrhit
Russian:Пирохлор
Simplified Chinese:烧绿石族
Spanish:Columbomicrolita
Koppita
Varieties:
Aluminobetafite (of Kawai)Bariopyrochlore (of Hogarth 1977)Bismutopyrochlore (of Chukanov et al.)Ceriopyrochlore (of Hogarth 1977)Plumbopyrochlore (of Skorobogatova et al.)
Stibiopyrochlore (of Pezzotta et al.)Strontiopyrochlore (of Hogarth 1977)Yttropyrochlore (of Hogarth 1977)Zero valent dominant member of Pyrochlore Group

Other Information

Health Warning:May be radioactive.

References for Pyrochlore Group

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.

Atencio D., Andrade M.B., Christy A.G., Giere R., Kartashov P.M. (2010): The pyrochlore supergroup of minerals: nomenclature. Canadian Mineralogist, 48, 569-594.

Christy, A. G. and Atencio, D. (2013): Clarification of status of species in the pyrochlore supergroup. Mineralogical Magazine, 77, 13-20.

Internet Links for Pyrochlore Group

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