Potassium autunite

All of the compounds with the autunite-type sheet sensu stricto are hydrates, with the sheets being held together mainly by hydrogen bonding. However, an interrupted autunite-type sheet has been reported in the anhydrous compound K4[(U02)(P04)2] [152]. Relative to the normal autunite-type uranyl phosphate sheet (Fig. 28), half of the uranyl square bipyramids are vacant (Fig. 37). Potassium atoms in the interlayer between the interrupted uranyl phosphate sheets provide charge balance and connectivity. 

Uranium is found in Earth s crust at an average concentration of about 2 ppm, and is more abundant than silver or mercnry. The most common uranium-containing mineral is uraninite, a complex nraninm oxide. Other uranium-containing minerals are autunite, a hydrated calcinm nranium phosphate, and carnotite, a hydrated potassium uranium vanadate. 

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