Abstract

Primary magnetite crystals occur in vugs and as a filling in leached iron-ore conglomerate found on the Mesabi Range, Minnesota. The associated minerals are marcasite, goethite, hematite, and siderite. The host material is a porous mechanical concentrate of the weathered underlying iron formation. It shows leaching, probably due to the activity of sulphate waters. Chemical reactions given indicate the possibilities that the magnetite is a precipitate from meteoric waters. Crystals grown in the laboratory under low pressure and temperature conditions are magnetic, and X-rays reveal the same diffraction pattern as that of magnetite from other sources. From the field investigation and from magnetite crystals developed in the laboratory the conclusion is drawn that magnetite can be formed as a precipitate from meteoric waters.

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