Great Britain was endowed with mineral wealth out of proportion to its small size. This is partly the result of its situation at the crossing-place of two of the three major European orogenic belts, the Caledonian and Hercynian, but perhaps more the result of the intense circulation of hot mineralizing fluids in systems of tension faults which were active at intervals from early Permian to Tertiary or possibly even to Neogene times. In the peninsula of Cornwall and Devon, tin, copper, tungsten and other non-ferrous metal deposits bear some relation to the Hercynian posttectonic granites. In areas of Lower Palaeozoic slaty rocks in central and northern Wales, the Lake District and the southern Uplands of Scotland, lead, zinc, and copper deposits occur, but many of them were emplaced in post-Carboniferous times. The Lower Carboniferous uplands of Mendip, north Wales, north Derbyshire and the northern Pennines are all highly mineralized, with lead and zinc, and in the Pennines fluorite, barite and witherite also appear in quantity. All deposits so far mentioned are epigenetic, i.e. emplaced later than the enclosing rocks. This also applies to the hematite deposits formerly worked in Carboniferous Limestone in west and south Cumberland and Furness, and those now working in south Wales. Mineral deposits which form part of the enclosing rock-sequence include the Permian dolomite-anhydrite-halite-sylvine evaporites of northeast England; the Triassic halite deposits particularly in Cheshire; and the siderite-chamosite ironstone in the Jurassic belt extending from Cleveland through Scunthorpe to Banbury. In addition, large tonnages of hard rocks are quarried in Scotland, Wales, northern and north-midland England and the Cornubian peninsula; and sand and gravel is worked from Pleistocene glacial deposits and Holocene alluvials, especially in the London district, East Anglia and the Trent valley.