The sand and gravel resources of the country east and south-east of Darlington, Durham : description of 1:25,000 sheet NZ 30 and 31

The geological maps of the Institute of Geological Sciences, pre-existing borehole information, and 120 boreholes drilled for the Industrial Minerals Assessment Unit form the basis of the assessment of the sand and gravel resources of the country east and south-east of Darlington, Durham. All the deposits in the district that might be potentially workable for sand and gravel have been investigated and a simple statistical method has been used to estimate the volume. The reliability of the volume estimates is given at the symmetrical 95 per cent probability level. The mineral bearing ground is divided into six resource blocks, containing between 2.3 and 14.3 km2 of potentially workable sand and gravel. For each block the geology of the deposits is described, and the mineral-bearing area, the mean thickness of overburden and mineral and the mean gradings are stated. Detailed borehole data are also given. The geology, the position of the boreholes and the outlines of the resource blocks are shown on the accompanying map.