in Norway and in Canada, 165 



The most important mines of the district south of Trondhjem, 

 are the copper mines of Roraas and its neighborhood, the chrome 

 mines on the Dovrefjeld, and the nickel mines of Espedal. 



The rocks around Roraas consist of micaceous slates, partly 

 chloritic, and partly argillaceous. They graduate into glossy clay 

 slates, and are sometimes described simply as green slates. These 

 frequently assume the character of fahlbands, being impregnated 

 with pyritous minerals, and weathering red. The deposits of 

 Roraas, which have been worked since 1744, seem to partake of 

 this nature. They form layers in the slates, varying from one to 

 fourteen feet in thickness ; the whole of which, however, by no 

 means consists of cupreous minerals, but usually of many small 

 pyritous beds, lying side by side ; these being again divided into 

 smaller ones, separated from each other by scales of chlorite 

 schist. The preponderating ores are copper pyrites, and iron 

 pyrites, which are sometimes mixed with magnetic pyrites and 

 zinc blende ; while chlorite, brown mica, quartz, garnet, actino- 

 lite, and asbestos, also accompany the metallic sulphurets. The 

 ores, as they are delivered to the smelting houses at Roraas and 

 Foldal, average only five per cent., and frequently are as low as 

 three per cent. They are roasted in heaps, and then smelted to reg- 

 ulus in shaft furnaces ; little or no flux being required. The result- 

 ing regulus is roasted repeatedly upon hearths, (stadeln) and again 

 smelted, when black copper is obtained, which is refined on the 

 small gahr hearth. The copper is principally sold for home con- 

 sumption, but part is also sent to the Hamburg market, where it 

 is known as " Drontheimer" copper. 



The chromic iron mines of Roraas in Sundal, and in Lessoe, 

 have been, and still are wrought with very considerable success. 

 They all occur in serpentine, and in one year as many as 100 have 

 been worked. Some of these are large and regular deposits, and 

 others are of less extent. The most important of them are situ- 

 ated in the districts to the east of Roraas, Rohararaerne, and Fer- 

 agsfjeldene, and are owned and worked by the proprietors of the 

 chromate of potash manufactory at Leren. Three different sorts 

 of ore are produced at the mine, : No. 1, the best, which is 

 exported to England, although its content in chromic oxide is 

 much beneath what is usually contained in the Baltimore ore; 

 No. 2, an inferior sort, which is worked up into bichromate of 

 potash at Leren ; No. 3 is a still poorer quality, which is stamped 

 and washed, the products being also used in the manufacture of 



