In this study, the origin and structure of the soluble organic matter in the phosphate rock was investigated. The organic matter was extracted with n-hexane from the phosphate rock. Its structure was analyzed by using TG, GC-MS, FTIR and NMR. GC-MS results showed that the organic matter had a complex structure and had a modal distribution ranging between C-9 to C-35 and maximizes at C-10 and C-14. The presence of n-alkanes with even/odd carbon predominance indicates the intense microbial reworking of the organic matter taking place in this depositional environment. The Carbon Preference Index (CPI) was 0.71 in which major microbial sources exist. H-1 NMR and C-13 NMR spectra of the phosphate rock also confirmed these results. FTIR results showed that the bands obtained from organic matter exhibits a phospholipid characteristic which is a component only of living cells and, as such, a measure of viable biomass.