At the Todhunter occurrence, a 1 to 1.5 metre thick chert- bearing conglomerate is exposed in a road cut. The conglomerate underlies Triassic rocks but the contact was not observed. The conglomerate is inferred to belong to the Permian Ishbel Group.

A grab sample of the conglomerate contained 2.1 per cent P2O5 (Open File 1987-16). Phosphate is contained in black pebbles.