THE ORIGIN OF TIN. 419 



The carboniferous limestone of the Parys mountain in Anglesea 

 has long been productive of copper ; and other mines in this for- 

 mation have been worked at Slanymyneck Hill in Shropshire, near 

 the Great Ormes Head, near Hartington, on the borders of Stafford- 

 shire and Derbyshire ; while there is an accumulation of bog copper 

 on the west of Khobell-fawr, near Dolgelly. Lodes of sulphide and 

 blue and green carbonate occur in the neighbourhood of Snowdon, 

 Beth-gelert, and Moel Hebog. The lead mines near Aberystwith are 

 charged with copper. In Ireland important mines occur in Avoca in 

 "Wicklow. Copper pyrites is the chief British ore. 



The Coniston copper mines of Cumberland are in Cambrian rocks. 

 They are principally copper pyrites found in quartz lodes running east 

 and west. 1 Similar deposits are found in Wicklow, and it is in rocks 

 of similar age that we find the native copper of Lake Superior, and 

 the Rio Tinto district in the south-west of Spain. The Devonian 

 rocks are nowhere richer in copper than in Cornwall and Devonshire. 



In many of the Cornish mines the copper pyrites is associated 

 with iron pyrites, and about Redruth copper succeeds tin in the 

 deeper part of the lode. In the west of Cornwall the grey sulphide 

 is associated with specular iron ore. 



Foreign Copper Mines. Copper is widely distributed in Europe, 

 chiefly in the Primary rocks. The Kupferschiefer of Thuringia is 

 worked as an ore of copper about Mansfeld in Prussia, where the rock 

 yields fifty pounds of copper to the ton. The Permian strata of Russia 

 are also copper-bearing, especially between Perm and Kazan. The 

 richer mines near Katherineburg are on the east side of the Ural, and 

 consist of lodes of copper pyrites with malachite in the upper part. 

 At Chessy near Lyons, the blue carbonate of copper was formerly 

 obtained from the base of the Permian sandstone. The principal 

 Italian copper ore is the sulphide found at several places in Tus- 

 cany, in serpentine and gabbro ; but the greatest copper-producing 

 districts of the world are in Chili between the 25th and 3oth paral- 

 lels, where the ore is found in volcanic rocks of Cretaceous age. 2 



Tin. 



DaubreVs Views on the Origin of Tin. Tin veins differ from 

 those of other metals in the ore being an oxide ; the gangue consists 

 of quartz, the tin is diffused in the quartz, and associated with wol- 

 fram and arsenical pyrites, besides which there occur various silicates, 

 fluorides, and borates, including lepidolite, topaz, pycnite, tourmaline, 

 and axinite. Apatite, a phospho-fluoride of lime, is common, and 

 accompanied by other phosphates. All over the world there is the 

 same association of tin with silica, fluor, boron, phosphorus, and 

 arsenic. M. Daubree urges that fluorine has been the chief agent, 

 not only in forming these minerals, but in bringing the tin to the 

 positions in which it is found. 



1 See Postlethwaite : "Mines and Mining in the Lake District," 1877. 



~ For many facts relating to Copper we are indebted to H. Bauerman, F.G.S. 



