On the sulfides in the sediments of the Bothnian Sea

Sediments starting with the Ancylus stage of the Baltic up to the Litorina stage contain considerable amounts of sulfide. Sulfide minerals of six samples were studied microscopically, chemically and by X-rays. Framboidal pyrite spherules occur in the sulfide-rich sediments whereas those with only sparse sulfide are black and contain pigmentous amorphic sulfide incorporated with colloids. Also marcasite-bearing framboidal spherules were verified. The chemical composition of the sulfides and also the size frequency distribution of the framboids are presented with diagrams.