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 Samarskite       Niobate and tantalate of            Primary constituent of                  rare earths                         pegmatite dikes Uranium 8-10%

Fergusonite      Metaniobate and tantalate                "      " of rare earths Uranium 1-6%

Euxenite         Niobate and titanate of                  "      " rare earths Uranium 3-10%

Monazite         Phosphate of the rare                    "      " earths, chiefly cerium Uranium 0·3-0·4%