Class : Oxides and hydroxides
    Subclass : Oxides
    Crystal system : Cubic
    Chemistry : (Na,Ca)₂Nb₂O₆(OH,F)
    Rarity : Fairly common

Pyrochlore is a complex oxide of niobium which forms a continuous series with microlite, a mineral in which tantalum replaces niobium. The pyrochlore group includes complex oxides with the general formula A₂B₂O₆(O,OH,F), with A = Ba, Bi, Ca, Ce, Cs, K, Na, Pb, Sb, Sn, Sr, Th, U, Y , Zr and B = Fe, Nb, Sn, Ta, Ti, W. Varieties rich in radioactive elements are commonly metamict and admit significant quantities of water. By uranium enrichment, we move on to betafite. Pyrochlore is found in granitic pegmatites and greisens, but especially in the pegmatites of nepheline syenites as well as in carbonatites. It is a resistant mineral that preserves well in alluvial deposits. Its name comes from the Greek pûr (fire) and khlôros (green) because the mineral turns green when heated. Pyrochlore is frequently crystallized, most often in octahedra that very rarely exceed 5 cm, but can adopt much more complex shapes by combination with the rhombododecahedron. The fracture is conchoidal to irregular, the color black to black-brown or dark red-brown, rarely red to vermilion. It is a mineral which is sometimes exploited as a rare earth and niobium ore : the alluvium deriving from the erosion of nepheline syenite massifs or alkaline complexes represent the main world reserves of niobium and tantalum.

Main photo : Pyrochlore from Vishnevye Mountains, Chelyabinsk, Russia © Knut Eldjarn

No twins known for this mineral species.

No fakes listed for this mineral species.