Mr. Kenwood's Notice of the Morro Velho Mine, 343 



being gradually replaced by quartzose and slaty substances 

 towards the sides of the vein, much as in many Cornish mines*. 

 Joints also sometimes interveneandgive a deceptive appearance 

 of distinct demarcations [smooth walls) between them; in such 

 cases, however, the mineral composition is much alike on both 

 sides of the joints f. On the upper side {hatiging wall) of the 

 great Quebra Panella the pyrites and the adjoining slate mutu- 

 ally penetrate each other, giving rise to a serrated appearance. 



e. The metallic minerals when brought to the surface are 

 spalled and stamped, as tin ores and the poorer copper ores 

 are in Cornwall; and the gold is afterwards separated from 

 the other ingredients by amalgamation. 



/. During the month of December 184-3, the pyrites ex- 

 tracted from the mine was 2168 tons, and it yielded 1 10 troy lbs. 

 of gold, or about 292 grains of gold from each ton of ore:}:. 



g. All the machinery is worked by water, and about 70 

 Europeans and 700 negroes are employed. 



h. The quantity of water in the mine is inconsiderable; at 

 about forty-two fathoms deep in the Bahu it issues from the 

 vein at a temperature of 68°; and somewhat shallower, in the 

 Eastern Cachoeira, at 69^. 



The richer portions of the vein at Morro Velho, as in all 

 other mines, are connected by vein-stones of a less metallic 

 composition. There are however four well-marked enlarge- 

 ments of it, which respectively preserve the same relative po- 

 sitions, the same configuration, and indeed almost exactly the 

 same dimensions, at every other portion of their descent yet 

 seen, as they expose in their outcrop at the surface. They 

 have a regular inclination of about 45° towards the E., on a 

 line which bears 2° N. of W. (magnetic) ; and this regularity 

 equally prevails, whether the dip of the vein may be parallel 

 or oblique to the cleavage of the containing rock, whether it 

 may be uniform or variable. 



A circumstance of value to the miner, as well as of interest 

 to the geologist, is however common to most, if not to all, of 

 the Brazilian mines ; namely, that whether the veins may be 

 parallel, transverse, or oblique to the schistose structure of the 

 rock, their sides (walls) are grooved or fluted with large striae, 

 which are coincident with the dips of the shoots of gold, both 

 in the angles and directions of their inclinations. 



These facts are most conspicuous at Morro Velho, where 

 the gold is dispersed through pyrites, and the rock is clay- 

 slate ; at Gongo Soco, where enormous masses of gold occur 



* Cornwall Geol. Tran?., vol. v. p. 185. f Ibid, p. 184. 



I Mining Journal, 1844, Mai'ch 16th. 



