Mendip Hills In some areas the limestone and the dolomitic conglomerate have been mineralised with lead and zinc ores. From the time of Roman Britain until 1908, the hills were an important source of lead. These areas were the centre of a major mining industry in the past and this is reflected in areas of contaminated rough ground known locally as "gruffy". The word "gruffy" is thought to derive from the grooves that were formed where the lead ore was extracted from veins near the surface. Other commodities obtained included calamine (zinc ore), manganese, iron, copper and baryte. The eastern area reaches
Thermo Electric Ore Reduction Corporation Mill the Hodgkinson River scattered over the surface as bunches in quartzose boulders or in drifts interspersed with coarse gravels. In 1900, 91 pounds of molybdenite was also discovered. This was said to contain some of the finest specimens of molybdenite discovered anywhere in Australia. Wolfram is composed of a heavy gray-white metallic element, with pure wolfram being used mainly in electrical applications and is also the ore from which tungsten is refined. In 1899 wolfram was returning £38 per ton. Other than along the Hodgkinson, wolfram has been located in north Queensland at Bamford Hill approximately west-south-west of Cairns in