Characterization of natural geological materials; lignite ...
collected in Java Island, Indonesia: lignite from Samigaluh, Kulon Progo area, Central Java and bentonite from Punung, Pacitan, East Java, shale from, Bogor, West Java; and iron sand from Glagah beach, Kulon Progo area. (Fig. 1). After collecting, these samples were brought back to the laboratory, airdried, crushed and sieved through 18
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