The northeastern part of the Comstock Property is underlain by andesitic volcanics of the Palaeozoic Index Formation. The south- western part is underlain by slates, greywackes, carbonates and volcanogenic sediments of the Broadview Formation. These formations formed a conformable eugeusynclinal sequence. Their boundary contact was originally gradational but is now a fault. The property contains the lower and upper Comstock workings. In the lower workings a 2 metre thick quartz vien is tested by 2 adits and trenches. This vein runs up to 19.3 ounces per ton silver and 30 per cent lead. At the upper workings at least two veins were explored by a series of trenches. The upper veins assay up to 35 ounces per ton silver.