Glauconite and phosphate from the Cenomanian of Devon, southwest England, may be classified into different groups on the basis of petrography. Chemical analysis of these different fabrics reveals a strong association between glauconite and phosphate occurring on a sub-microscopic scale. Despite this intimate association, certain deductions may be made about the mineralogy of the glauconite (notably the K concentration) and its relationship to its morphology. Glauconite and phosphate formation took place in the transitional zone between oxic and anoxic environments (suboxic zone). Iron oxyhydroxides were a potential source of phosphorus and iron, while 'sulphide fluxing' maintained pH levels appropriate for carbonate dissolution and subsequent mineralisation.