A selenate selenite is a chemical compound or salt that contains selenite and selenate anions (SeO32- and SeO42-).
One way to produce a selenate selenite compound is to evaporate a water solution of selenate and selenite compounds.
[1] On heating, selenate selenites lose SeO2 and O2 and yield selenites, and ultimately metal oxides.
[2] Related to these are the sulfate sulfites and tellurate tellurites.
They can be classed as mixed valent compounds.