In view of observations coal surface could be visualized to consist of a patchwise structure as shown schematically in Figure 10. ... not yet oxidized, patches (hp), hydrophi- lic, oxidized patches (ox) and silica or mineral matter containing hydrophllic (min) patches. ... 80, pp. C199-C200. 3. Jowett, A., (1958), aquot;Influence of Frother Agent on Percentage Recovery of Coal From Flotation Pulpsaquot;, J. Inst. Fuel, Vol.