TIN 



1001 



1982 



Fig, 1982 represents a vertical section of the Pentewan deposit, taken from the 

 stream-work Happy Union, long since abandoned. A vast excavation, B, T, v, e, has 

 been hollowed out in the open air, in quest of the alluvial tin ore T, which occurs here at 

 an unusual depth, below the level of the strata B, s. Before getting at this deposit, 

 several successive layers had to be sunk through, namely, 1, 2, 3, the gravel, containing 

 in its middle a band of ochreous earth, 2, or ferruginous clay ; 4, a black peat, perfectly 

 combustible, of a coarse texture, composed of reeds and woody fibres, cemented into 

 a mass by a fine loam ; 5, coarse sea-sand, mingled with marine shells ; 6, a blackish 

 marine mud, filled with shells. Below these the deposit of tin-stone occurs, including 

 fragments of various size, of clay-slate, flinty slate, quartz, iron ore, jasper; in a word, 

 of all the rocks and gangues to be met 

 with in the surrounding territory, 

 with the exception of granite. Among 

 these fragments there occurred, in ' 

 rounded particles, a coarse quartzose' 

 sand, and the tin-stone, commonly 

 in small grains and crystals. I 

 neath the bed T, is the clay-slate 

 called killas (A, x, T), which supports 

 all the deposits of more recent forma- 

 tion. 



The system of mining employed 

 in stream-works is very simple. The 

 successive beds, whose thickness is shown in the figure, are visibly cut out into steps 

 or platforms. By a level or gallery of efflux k, the waters flow into the bottom of 

 the well I, m, which contains the drainage pumps ; and these are put in action by a 

 machine j, moved by a water-wheel. The extraction of the ore is effected by an 

 inclined plane i, cut out of one of the sides of the excavation, at an angle of about 45 

 degrees. At the lower end of this sloping pathway there is a place of loading ; and 

 at its upper end h, a horse-gin, for alternately raising and lowering the two baskets of 

 extraction on the pathway i. 



Mine-tin as distinguished from Stream-tin, the former being worked by the miner 

 out of the lode requires peculiar care in its mechanical preparation or dressing, on 

 account of the presence of foreign metals, from which, as we have stated, stream-tin 

 is free. 



Tin ore, therefore, should be first of all pounded very fine in the stamp-mill, then 

 subjected to reiterated washings, and afterwards calcined. The order of proceeding 

 in Cornwall and other parts is fully described in the article DRESSING OF OKES. 

 See also BOASTING, for a description of the roasting processes. 



The tin ores of Cornwall and Devonshire are all smelted within the counties where 

 they are mined : the vessels which bring the fuel from Wales, for smelting these ores, 

 return to Swansea and Neath loaded with copper ores. , 



Australian Tin. As far back as 1 849 the Rev. W. B. Clarke, from the character of 

 certain granites, predicted the occurrence of tin in New South Wales ; and in 1853 he 

 reported the actual discovery of tin ore near the Severn River. It was not, however, 

 until recently that the tin ore of New South Wales and Queensland has been found 

 in sufficient abundance to attract general attention. In New South Wales the tin- 

 yielding district forms an elevated plateau of granitic rocks, associated with meta- 

 morphic slates and sandstones. The granite is, in places, traversed by veins of 

 quartz, rich in tin-stone, and is capped by a deposit of tin-bearing detritus of variable 

 thickness. The stanniferous district extends into the adjacent colony of Queensland, 

 the ore having been traced over an area of about 550 square miles in the neighbour- 

 hood of the head-waters of the Severn River and its tributaries. The Queensland 

 tin occurs partly in lodes associated with granitic rocks, and partly as stream-tin in 

 beds of the rivers and in the alluvial flats on their banks. 



From these new districts the following quantities have been obtained : 



In Victoria. Tin has been found in the districts of Beechworth, Koetong, Upper 

 Murray, Burrawa Creek, Yackandandah, Cudgewa Creek, La Trobe River, Corner 

 Inlet, Chiltern, Mansfield, Foster, and Omea. In all cases the black tin has been 

 obtained from alluvial deposits generally termed ' black sand.' The quantity of tin 

 produced in Victoria up to the end of 1873 has been as follows : 



Previously up to December 31, 1872 

 From January 1 to December 31, 1873 



Total 



Tin Ore 

 Tons Cwts. 

 3,831 16 

 174 16 



4,006 12 



Tin 



Ibs. 



139,648 

 109.312 

 248,960 



