Disclosed is a process for removing mineral matter from oil-shale which method comprises contacting the oil-shale with (a) an ammonium salt solution, and (b) a nonionic surfactant at a temperature from about 0.degree. C. to about 300.degree. C. for a time which is sufficient to substantially separate at least about 80 wt. % of the carbonate mineral matter of the oil-shale.