Series of beach ridges are of Holocene age, ranging in age from 6600 years to present and composed predominantly of shell fragments, average 78% calcium carbonate. Total recorded production from the deposits is 1.16 million tonnes. Auger drilling of 439 holes averaging 1.5 million has shown total shell grit reserves to be 22 million tonnes, of which all but 3.5 million lie within the 800 metre coast zone'. Of the reserves available for mining, 0.6 million lies outside existing tenements. Future demand may be for glass manufacture from the ACI leases at Lorne, for agricultural lime, and for cement manufacture, the latter 2 to be supplied largely from the Camberwarra leases at Port Prime.