HEXAVALENT-URANIUM PHOSPHATE MINERALS

The hexavalent-uranium phosphate minerals (Table 14) are important and widespread uranyl-oxysalt minerals. Their structures and behavior are dominated by the crystal chemistry of the (U 02) uranyl group they have been described in detail by Burns (1999) and will not be considered any further here. 

Huminicki Hawthorne Table 12. Minerals with apatite-like struetures. 

---

Precipitation occurs as a result of the reduction of the hexavalent ion to a tretravalent ion with modification of pH, pressure, temperature, etc. Uranium is fixed by clay minerals, iron and manganese hydroxides, phosphates and organic matter. 

---