8 Macfarlane on the Primitive Formations 



they are comparatively rare. Besides these, cobalt glance, co- 

 baltiferous arsenical, and iron pyrites, nickeliferous magnetic 

 pyrites, and argentiferous iron pyrites characterise peculiar lo- 

 calities. The impregnation seems to be altogether independent of 

 the nature of the rock ; gneiss, mica schist, hornblende schist, <fec., 

 being alike found constituting fahlbands. The continuity of these 

 impregnated zones is frequently astonishing, some of them hav- 

 ing been traced in the direction of their strike, nearly north and 

 south, upwards of ten miles. Their course is often marked by 

 depressions in the rocks, caused by their greater proneness to de- 

 composition, and these depressions are frequently occupied by 

 marshes and lakes. The thickness of these bands varies 

 from a few feet to several hundred, and they have been fre- 

 quently observed to split up and throw oflf side bands, some 

 of which seem to connect with other similar zones. Although, 

 as in the case of the glance cobalt and cobaltiferous mispickel, 

 the impregnating material is sometimes the object of mining 

 enterprise, it is generally on the veins or irregular masses occur- 

 ring in these fahlbands, that the mines of the district are situ- 

 ated. Concentrations of metallic sulphurets or other minerals in 

 fissures parallel with or crossing the strata, are by no means un- 

 common, and in some instances have given rise to very profitable 

 mining. The metallic deposits which I propose to notice in con- 

 nection with those fahlbands, are the silver mines of Kongsberg, 

 the copper mines of Eker, the cobalt mines of Skuterud, and the 

 nickel mines of Kingerike, all of which are at present being 

 worked. 



The rocks in which the fahlbands of Kongsberg occur are 

 gneiss, mica schist and hornblende schist ; other rocks, such as 

 granite, talc schist and chlorite-schist, granitic gneiss and green- 

 stones occur also in the immediate neighbourhood. Seven differ- 

 ent fahlbands or groups of fahlbands have been recognized as 

 existing in these rocks around Kongsberg, on every one of which, 

 at some time or other since the year 1623, more or less mining 

 has taken place. The two fahlbands which have been most mi- 

 nutely examined, have an average thickness, respectively, of 200 

 feet and 1100 feet. The impregnating sulphurets are iron pyrites, 

 magnetic and copper pyrites ; some of which appear to be argen- 

 tiferous, since the fahlband itself contains one-eighth of an ounce 

 silver per cwt. These fahlbands are intersected throughout the 

 whole extent, about six miles, by numerous veins containing gen- 



