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To complete our picture of the mineral wealth of Spanish America, it remains tospeak of its principal gold mines; hut these belong to a geological locality, alluvial sandsand gravel, very different from that of our present objects. The most important of thesegold sands are washed on the western slope of the Cordilleras; viz., in New Grenada ,from the province of Barbacoas, to the isthmus of Panama , to Chili, and even to theshores of the seas of California . There are likewise some on the eastern slope of theCordilleras, in the high valley of the river Amazons. The washings of New Granada produce also some platina.
The mines, properly so called, and the washings of South America , furnish, altogether,42,575 marcs, or 10,418 kilogrammes (22,920 libs. Eng.) of gold, worth 1,435,720/.
The metallic mines of this kingdom, including those of Transylvania , and-the Bannatof Temeschwar , form four principal groups, which we shall denote by the group of theN.W., group of the N.E., group of the E., and group of the S.E.
The group of the N.W. embraces the districts of Schemnitz, Kremnitz , Koenigsberg,Neuhsohl, and the environs of Schmoelnitz, Bethler, Rosenau, &c.
Schemnitz, a royal free city of mines, and the principal centre of the mines of Hun-gary , lies 25 leagues to the north of Buda, 560 yards above the sea, in the midst of asmall group of mountains covered with forests. The most part of these mountains, thehighest of which reaches an elevation of 1,130 yards above the ocean, are formed ofbarren trachytes (rough trap rocks); but at their foot below the trachytic formation,a formation is observed, consisting of green-stone porphyries, connected with syenites,passing into granite and gneiss, and including subordinate beds of mica-slate and lime-stone. It is in this formation that all the mines occur.
It has been long known that the green-stone porphyries of Schemnitz have intimaterelations with the metalliferous porphyries of South America . M. Beudant, on com-paring them with those brought by M. de Humboldt from Guanaxuato, Real del Monte,&c., has recognised an identity in the minutest details of color, structure, composition,respective situation of the different varieties, and even in the empirical character ofeffervescence with acids. The metalliferous rocks appear at Schemnitz only in a spaceof small extent, comprehended partly in a small basin, of which the city occupies thesouth border. They are traversed by veins which, for the most part, cut across the strati-fication, but which also are sometimes obviously parallel to it. These veins are ingeneral very powerful; their thickness amounting even to more than 40 yards, but theirextent in length seems to be usually inconsiderable. They are numerous and parallelto each other. It appears that they have no side plates of vein-stones ( sallebandes ), butthat the metalliferous mass reposes immediately on the cheeks or sections of the rock,Which is usually more or less altered, and includes always much pyrites near the pointof contact, and even to a distance of several feet. The substances which constitute thebody of these veins, are drusy quartz, carious quartz, ferriferous carbonate of lime, andsulphate of barytes, with which occur sulphuret of silver mixed with native silverContaining more or less gold, which is rarely in visible scales; sulphuret of silver, argen-tiferous galena, blende, copper and iron pyrites, &c. The sulphuret of silver and thegalena are the two most important ores. Sometimes these two substances-are insulated,sometimes they are mixed in different manners so as to furnish ores of every degree ofrich ness, from such as yield 60 per cent, of silver down to the poorest galena. The goldseldom occurs alone; it generally accompanies the silver in a very variable proportion,Which most usually approaches to that of 1 to 30.
The ores of Schemnitz are all treated by fusion; the poor galenas at the smeltingbouse of Schemnitz (bleyhutte), and the resulting lead is sent as working lead to thesutelting-houses of Kremnitz , Neusohl, and Schernowitz, whither all the silver oresPrepared in the different spots of the country are transported in order to be smelted.
The mines of Schemnitz , opened 800 years ago, have been worked to a depth of morethan 350 yards. The explorations are in general well conducted. Excellent galleriesof efflux have been excavated; the waters for impulsion are collected and applied'with skill. It may be remarked, however, that these mines begin to decline from thestate of prosperity in which they stood several years ago ; a circumstance to be ascribedUrobably to the same pains being no longer bestowed on the instruction of the officers’"^pointed to superintend them. Maria Theresa established in 1760, at Schemnitz , aschool of mines. This acquired at its origin, throughout Europe , a great celebrity,Which it has not been able to maintain.
Kremnitz lies about five leagues N.N.W. of Schemnitz , in a valley Hanked on theWght by a range of hills formed of rocks quite analogous to the metalliferous rocks ofSchemnitz . In the midst of these rocks, veins are worked nearly similar to those ofSchemnitz ; but the quartz which forms their principal mass is more abundant, and con-tains more native gold. Here also.are found sulphuret and hydrosulphuret of antimony*.