The geochemistry and mineralogy of the potential phospharite deposits recovered from the continental margin off Chennai, Tamil Nadu (India) and their comparison with other offshore phosphorites is given. The phosphorites recovered are classified into four types as (1) light brown friable phosphorites (2) grey dense phosphorites (3) phosphorite sands and (4) phosphatized algal nodules/limestones. Major element composition of phosphorites indicate that the P@d2@@ O@d5@@ content is highest (31%) in phophorite grains (phosphorite sands) followed by friable phosphorites (27%) and dense phosphorites (21%) and least in algal nodules (9%). Carbonate fluorapatite and calcite are the major minerals in friable phosphorites, dense phosphorites and phosphorite sands. Quartz, feldspar and high magnesium calcite are the accessory minerals. EDAX (energy dispersive x-ray analysis) carried out for 9 elements on JEOL 840 SEM/EDAX, reveal that measurable S contents (0.9%) occur in only algal nodules.