A petrographic study has been made of a column sample and of crushed commercially delivered lignite from Dakota Collieries mine, Zap, Mercer County, North Dakota. A technique has been developed for preparing thin sections of samples of the crushed lignite by embedding the particles in plaster of Paris with a plastic resin binder and then using conventional polishing techniques. Microscopic analysis was made by the usual Bureau of Mines petrographic method, slightly modified. Evidence is presented that results of such an investigation of crushed delivered lignite are closely comparable with an overall analysis of a column sample and that this method can be used for a petrographic survey of the delivered product of lignite mines.

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