A source of railway ballast was sought in the Barunga Sandstone of Upper Proterozoic age which underlies the Hummock Range, Barunga Range and other low lying hills in the midnorth of South Australia. Green clay occurring as interbeds and as joint fillings has caused difficulties in working earlier quarries in the area and initial exploration was designed to locate a site free of this material. Trenching and drilling of one diamond drill hole in section 165 Hundred of Goyder, 3.7 km (2.3 miles) southeast of Nantawarra, has shown 3 metres (90.66 feet) of Barunga Sandstone unit. The latter consists of 86% quartzitic sandstone suited for ballast and 14% clay material which would be deleterious in crushed rock. One diamond drill hole in section Hundred of Everard, 3.2 km (2.0 miles) east of Bumbunga, intersected 16.50 metres (54.12 feet) of Barunga Sandstone unit. This consisted of 72% quartzitic sandstone suited for ballast and 28% clay material which would be deleterious in crushed rock. However, to a depth of 8.00 metres (26.24 feet) only 3% clay material is present. Both sites have been abandoned after consultation with South Australian Railways engineering personnel.