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Formula: (Pb1.5☐0.5)Nb2O6(OH)
Oxide, pyrochlore group,
niobium-bearing mineral
Crystal System: Isometric
Specific gravity: 6.474 calculated
Hardness: 5½
Streak: White
Colour: Pale yellow to pale brown
Luminescence: Non-fluorescent in UV
Environments
Plutonic igneous environments
Pegmatites
The first find of hydroxyplumbopyrochlore was made in 1992 on Khaldzan Buragtag massif, Altai Mts, Hovd Aimag,
Mongolia. It was approved in 2020, with the type locality being the Jabal Sayid peralkaline granitic complex, Saudi
Arabia
(Mindat).
Localities
At the type locality, the Jabal Sayid mine, Medina Region, Saudi Arabia, hydroxyplumbopyrochlore has been
discovered in
pegmatite-aplite
rocks of the peralkaline granitic complex. It is associated with
quartz,
microcline, biotite,
rutile, zircon,
calcite, rhodochrosite,
columbite-(Fe), goethite,
thorite, bastnäsite-(Ce),
xenotime-(Y), samarskite-(Y),
euxenite-(Y),
hydropyrochlore and
fluornatropyrochlore. Hydroxyplumbopyrochlore usually
shows pale yellow to pale brown, euhedral octahedra, slightly rhombic dodecahedra and cubes or their combination
(0.01–0.06 mm)
(MM 84.5.785-790).
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