In the mountain wilds between Tysfjord and Ofotenfjord in northern Norway, where the rock is exceedingly well exposed, we frequently observe small, rounded knolls of a reddish-brown or yellowish- brown hue, visible at a great distance. Fig. 1.
They are lacking every trace of vegetation and their smooth surfaces retain the glacial striæ better than any other rock. They consist of more or less serpentinized olivine rocks, and their generally massive structure is in a peculiar contrast with the toliation structure of the mica schists, amphibolites and other sedimentary and igneous crystalline schists of Palæozoic age, which constitute the region.
Notwithstanding their great number, these serpentine bosses - as we might call them - are quite subordinate in quantity, the individual bosses having diameters only from 10 to a couple of hundred meters.
They nearly look like drops, having an elongated to nearly circular outline, as well in vertical as in horizontal sections, and are not lenses, because the ends are always rounded. The major part of them occur within amphibolite bands (metamorphosed gabbros), and the general distribution leaves no doubt about their consanguinity to the other Caledonian intrusives of the region. They are also found over wide regions within the Caledonian mountain chain of northern Norway and Sweden.