Biotitt-søvitt på Stjernøy, Vest-Finnmark.

Abstract

The island of Stjernøy is built up of a complex of gabbroid rocks, which in the valley of Fjellfinndalen (fig. 1) surrounds a body of chiefly calcite-biotite rock more than commonly rich in apatite, clearly of non-sedimentary origin and thus to be classed as s\u00CEvite. The chemical and mineral composition of this rock can be obtained from the chemical and geometrical analyses pp. 15-19. Albite-biotite pegmatites and hornblendites are common as dykes and veins in the s\u00CEvite. Of more rare occurrence are veins of nepheline syenite and ultrabasic olivine-bearing rocks. The contents of the apatite in the s\u00CEvite vary between 1 per cent and just over 10 per cent, with a probable average of about 4 per cent. As far as is known at present no part of the rock is rich enough in apatite to be of economic interest as a phosphate deposit.