OIESECK^ ON THE GEOLOGY OP GREENLAND. 329 



very frequently met with in the mountains of Greenland. Most 

 of the granitic rocks affect the needle. 



2. The next rock which forms numerous mountains in this conntry 

 is Gneiss. It occurs very often alternating with granite, some- 

 times with mica-slate. Its character or texture may be ascertained 

 partly in the cliffs and on the shores, partly by the forms of the 

 mountains. The granitic mountains are|always more decomposed and 

 therefore more precipitous, presenting veiy sharp-edged summits ; 

 the summits of the gneiss are more flat and round-backed. The 

 texture of the. gneiss is thick- and thin- slaty ; its felspar generally 

 penrl-grey and pearl-white, seldom flesh-red, fine-granular ; its 

 mica-grey, pinchbeck-brown, and blackish-brown ; it contains but 

 little ash-grey quartz. The valleys and clefts round the mountains 

 are filled with rhomboidal fragments, many of them of immense 

 size. The smaller fragments were used by the old Norwegians, 

 with mica-slate, hornblende-slate, and slaty claystone to build 

 their houses ; the walls of which, although not cemented, after a 

 lapse of several centuries still brave the power of this destructive 

 climate. Gneiss constitutes one of the most elevated points of 

 this extensive coast, viz., the mountain Kingiktorsoak, situated in 

 the 62nd degree of latitude. It is covered with mica-slate from 

 the shore to a height of about 1,000 feet above the level of the 

 sea, where tlie gneiss again becomes visible, and continues to a 

 height of nearly 3,000 feet. The top of this mountain is similar 

 in shape to the roof of a house, where the ridge is not much ele- 

 vated. It is entirely free from snow in summer, except a few 

 small spots, where it rests in the hollows of its summit. 



The mica-slate resting upon the gneiss presents a variety of 

 beds of hornblende-slate, whitestone (Weiss-stein) with small 

 garnets, talc-slate with common and indurated talc, potstone, acty- 

 nolite, and precious splintery serpentine. The gneiss is transversed 

 with numerous veins of greenstone, various in thickness from one 

 inch to six feet. The greenstone which occurs in the veins re- 

 sembles basalt ; but it is more crystalline in its texture, lighter 

 in its colour, and not quite so hard. Common schorl, tourmaline, 

 and precious garnet occur imbedded in gneiss. It contains veins 

 of tinstone, accompanied by arsenical pyrites, wolfram, fluor, and 

 quartz, in a firth called Arksut, situated about 30 leagues from 

 the colony of Juliana-Hope, towards north-east. The same place 

 is remarkable for two thin layers of cryolite, resting upon gneiss ; 

 and it is the only place where this mineral has hitherto been found. 

 One of these layers contains the snow-v/hite and greyish-white 

 variety, unmixed Avith any other mineral. Its thickness varies 

 from one foot to two feet and a half; and it is divided from the 

 underlying gneiss by a thin layer of mica, always in a state of 

 disintegration. The other variety is of a yellowish -brown colour, 

 passing into tile-red. It occurs along with iron-pyrites, liver- 

 brown sparry-iron-ore crystallised in rhombs, earthy cryolite, 

 quartz, compact and foliated fluor, earthy fluor, and galena. It 

 is remarkable that the galena is sometimes coated with a greyish- 

 white sulphureous crust, which burns in the flame of a candle 

 with a bluish colour, emitting a sulphureous smell. 



