The major portion of Thanjavur district is covered by Cauvery Alluvium and reported to have potential for mineral wealth. Vallam stones, laterite, sandstone, Kankar and yellow ochre have been reported from the District. Quartz crystals rolled into pebbles occur in the tertiary formation. Iron ore is found to exist in the neighbourhood of Vallam. Vallam area in Thanjavur Taluk yield laterite of fine quality. Pebbles of transparent quartz occur in conglomeratic sandstones near Vallam. These are of the amethystine citrine and smoky varieties.

Kankar and tuffaceous limestones occur under redsoil laterite ranging in the thickness from 0.3 to 1.0 m. Kankar layers are also noticed in stream sections. The important occurrences are seen in the Grand Anicut canal cutting between Kuruvadipatti and Pudur and also in the neighbourhood of Thirumalaisamudram. The thickness of Kankar in Thirumalaisamudram area ranges from 2.0 to 2.5 metres and the total reserves have been estimated to be about 0.5 million tonnes. The Kankar is of good quality, coal ranging from 48.42 percent to 52.72 percent and low in Magnesia.