COPPER 911 



Copper in 100 



5. Red oxide of copper, Cu*0 88'5 



6. Malachite. 2CuO,C0 2 + HO 57'4 



7. Azurite, 2(CuO,C0 2 ) + CuO,HO 55'3 



We shall here give a brief account of the copper slates of Mansfeld, in Prussia, 

 and of the copper veins of Cornwall. 



Copper-slate (Kupferschiefer) of Mansfeld, in Prussian Saxony. The Kupferschiefer 

 is a dark coloured bituminous schist, impregnated with copper ore, occurring with 

 singular persistence over a large area on the south-east of the Hartz. Its geological 

 position is in the Permian formation, below the Zechstein, or Magnesian limestone, 

 and above the red sandstones and conglomerates known as the Eothtodtliegendc ; 

 indeed, the latter name (' red dead strata') has reference to the fact that the ores in the 

 overlying schist die away on approaching these beds. The actual floor of the cupreous 

 schist is formed by a thin bed of white sandstone, known as the Weissliegendes, the 

 upper part of which is slightly cupriferous, and is smelted under the name of Sanders. 

 Upon this sandstone rest the true copper-bearing schists, forming three or four thin 

 beds, with an aggregate thickness rarely exceeding two feet, and sometimes not 

 attaining more than half this thickness. The schists care highly fossiliferous, and arc 

 especially rich in remains of ganoid fish belonging to the genera Paleeoniscus and 

 Platysomus. Towards their upper part, the schists become calcareous, and are some- 

 times known as the Noberge. The beds of cupreous schists, or copper-slate, are thrown 

 into a synclinal form, and are chiefly worked near their basset ; the intrusion of 

 masses of melaphyre has divided the deposit into three separate areas : those of 

 Eisleben, Sangerhausen, and Frankenhausen. The schist is richest in the neighbour- 

 hood of faults, and the thinner beds are said to hold more copper than the thicker 

 deposits. Only a few inches not generally more than five are worth working. 

 The ore is disseminated in the form of copper pyrites, copper-glance, and purple-ore. 

 The schist contains from 1-8 to 37 per cent, of copper, and this copper always con- 

 tains traces of silver, 1 cwt. of copper holding from 0-53 to 0'58 Ib. of silver. 

 Although the German copper-slate is thus a very poor ore, yet by an admirable 

 organisation of the mines and smelting-works both the copper and pilver are profitably 

 extracted, and a large population entirely supported by this industry. The copper- 

 mines of Mansfeld have been worked since the close of the twelfth century ; Martin 

 Luther's father was a miner in this district. The metallurgical treatment of the 

 copper-slate will be described below. 



Cornish Copper Veins. The deposits of copper in Cornwall occur as veins in 

 granite, or in the schistose rocks which surround and cover it ; and hence, the Cornish 

 miners work mostly in the granite and clay-slate ; the former of which, when metalli- 

 ferous, is usually in a coarse and often a disintegrated state ; this they call growan, 

 the latter killas. 



Copper veins are abundant in killas and more rare in granite ; but most numerous 

 near the line of junction of the two rocks. The different kinds of copper veins in 

 Cornwall may be classed as follow : 



1. Copper veins, generally running east and west. 



2. Second system of copper veins, or contra lodes. 



3. Crossing veins ; cross-courses. 



4. Clay veins, called Cross-Flookans or Slides. 



The width of these veins does not often exceed 6 feet, though occasional enlarge- 

 ments to the extent of 12 or more feet sometimes take place. Their length is unknown, 

 but one explored in the United Mines has been traced over an extent of seven miles. 

 The gangue of these veins is generally quartz, either pure, or mixed with green 

 particles analogous to chlorite. They contain iron pyrites, blende, sulphide, and several 

 other compounds of copper, such as the carbonate, phosphate, arsenate, chloride, &c. 

 The most part of the copper lodes are accompanied by small argillaceous veins, called 

 by the miners flookans of the lode. These are often found on both sides of the vein, 

 so as to form cheeks or watts. 



When two veins intersect each other, the direction of the one thrown out becomes 

 an object of interest to the miner. In Saxony it is regarded as a general fact, that the 

 rejected portion is always on the side of the obtuse angle ; this also holds generally in 

 Cornwall, and the more obtuse the angle of incidence, the more considerable the heave. 

 The great copper vein of Carharack, in the parish of Gwennap, is an instructive ex- 

 ample of intersection. The width of this vein is 8 feet ; it runs nearly from east to 

 west, and dips towards the north at an inclination of 2 feet in a fathom. Its upper 

 part is in the killas, its lower in granite. This vein has suffered two intersections : 

 the first results from encountering the vein called Steven's flookan, which runs from 

 north-east to south-west, throwing it out several fathoms. The second has been caused 

 by another vein, almost at right angles to the first, and which has heaved it 20 fathoms 



