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
Bioabsorbable metallic glass numerous ternary alloys along the 350 °C isotherm of the Mg-Zn-Ca system. Ternary Ca-Mg-Zn bulk metallic glasses were also discovered in 2005. Similar to the Mg-Zn-Ca, these two amorphous alloys are both bioresorbable metallic glasses and are based on the same "Mg-Zn-Ca ternary system". The elements are displayed in order of decreasing atomic concentration. Hence, the distinction between these two metallic glasses lies in their most dominant element, namely Ca and Mg. These Ca-based bulk glassy alloys had compositions of CaMgZn, CaMgZn, and CaMgZn, where X = 0, 5 and 10; Y = 0, 5, 7.5, 10, and 15; and