title: Graphitization of Organic Material in a Progressively Metamorphosed Precambrian Iron Formation.
abstract: Organic matter in the sedimentary Biwabik iron formation in northern Minnesota shows a progressive increase in crystallinity where the formation is metamorphosed by the intrusive Duluth gabbro complex. X-ray diffraction of acid-insoluble residues shows that there is a complete range in crystallinity, from amorphous material in the unmetamorphosed sediments to completely crystalline graphite adjacent to the gabbro.
authors.forename: B M
authors.initials: BM
authors.lastname: French