OF THE EIO-TINTO MTl^^ES. 257 



combination of the two. Rarely the crystals reach the size of 

 peas, but usually they are minute. This is absolutely valueless 

 (" esteril "). 



d. A soft powdery or easily pulverized substance, having the same 

 composition as the poor ore «, but valueless on account of its powdery 

 condition. 



The particles under a lens appear to be crystals. This is known 

 as " azufron." Sometimes the crystals are coated superficially with 

 galena or blende, as if they had been immersed in water capable of 

 depositing those substances. 



e. Compact ore like «, but containing from 1 to 2| per cent, of 

 copper, existing as copper-pyrites minutely disseminated throughout 

 the mass. This is the typical " telera mineral," and it is mostly 

 treated on the spot. 



/. Compact ore like e but richer, up to 3j per cent. This is the 

 typical exportation ore so largely consumed in the manufacture of 

 sulphuric acid, the copper, and sometimes the silver and gold, being 

 afterwards extracted by "wet"' methods. 



g. Ore similar to /, but coated superficially or in the joints by 

 basic sulphates of copper (brochantite, pisanite, &c.). This is also 

 an exportation ore. • 



h. Copper-pyrites, erubescite, and occasionally copper-glance, more 

 or less mixed with iron-pyrites, quartz, blende, and other substances, 

 occurring for the most part in veins or veinules traversing the ordinary 

 pyrites. These assay from 4 per cent, up to from 12 to 14 per cent. 

 en masse, and are aU treated in the blast-furnaces, either raw or 

 previously calcined, as " mineral rico." 



i. The same ore, but with much quartz present, reducing the 

 percentage to 3 or 4 per cent. Valuable as a flux in the blast- 

 furnaces ("mineral cuarzo"). 



j. Mineral like h, but very soft and much decomposed. Also 

 remitted to the blast-furnaces, under the name of " negrillo." 



Jc. A compact mixture of galena, blende, and chalcopyrite, 

 mingled with iron pyrites, yielding from. 6 to 12 per cent, of lead 

 and the same of zinc, with 3 or 4 per cent, of copper and 2 to 3 oz. 

 of silver to the ton ; known as " plomizos," and at present a hete 

 noire at the mine. Some of this bears a considerable resemblance 

 to the " bluestone " of Anglesey and to the " kilmacooite " of 

 County Wicklow. 



Z. The same, but with the lead more differentiated into veins of 

 galena, admitting of dressing or clean hand-picking. There is but 

 little of this ore in the mines. 



m. Crystals, stalactites, or stalagmites of cupreous melanterite, 

 containing from 4 to 12 per cent, of copper and from 2 to 10 per 

 cent, of zinc. Often mixed with earthy matter, so that the copper 

 is reduced to from 1 to 3 per cent. This is sent at once to the 

 washing-tanks, under the name of " vitriolas." 



n, 0. Porpyhry and slate, containing grains or veins of iron- 

 pyrites; slightly cupriferous ("esteril"). 



The varieties 6, c, and d appear to reveal much as to their mode of 



