naa a22 4500 510755852 CHVBK 20180411083122.0 cr unu---uuuuu 180411e20130201xx s 000 0 eng 10.1007/s12594-013-0023-9 doi (NATIONALLICENCE)springer-10.1007/s12594-013-0023-9 Nayak Bibhuranjan CSIR National Metallurgical Laboratory, 831 007, Jamshedpur, India aut Mineral matter and the nature of pyrite in some high-sulfur tertiary coals of Meghalaya, northeast India [Elektronische Daten] [Bibhuranjan Nayak] Coal samples collected from four different sources in the Jaintia Hills of Meghalaya, northeast India, have been investigated for their sulfur content, mineral matter, and to assess their potential behavior upon beneficiation. These coals contain high sulfur which occurs both in organic and inorganic forms. The organic sulfur content is much higher than the inorganic sulfur. Studies on different size and gravity fractions indicated that the mineral phases are concentrated in higher density fractions (d > 1.8) and in general are fine grained (<50 μm). Data of reflected-light optical microscope and electron probe micro-analysis (EPMA) revealed that minerals in these coals are sulfides-pyrite, marcasite, sphalerite, pentlandite; sulfates-barite, jarosite; oxides-hematite, rutile; hydroxides-gibbsite, goethite; phosphate-monazite; carbonate-calcite, siderite and silicates-quartz, mica, chlorite, and kaolinitic clay. The disulfides of iron occur in two modes — mainly pyrite and occasionally marcasite with wide size ranges and in various forms, such as: framboid, colloidal precipitate, colloform-banded, fine disseminations, discrete grains, dendritic (feathery), recrystallized, nuggets, discoidal, massive, cavity-fracture- and cleat-fillings. Framboidal pyrite has formed primarily due to biological activities of sulfur reducing bacteria in the early stages of coalification. Massive and other varieties have formed at later stages due to coalescence and recrystallization of the earlier formed pyrites. Sulfur isotopic values indicate a biogenic origin for the pyrites. Association of trace metals, such as Ni, and Zn has been recorded in these pyrites. Given the large fractions of organic sulfur present, these coals can be upgraded only partially to reduce the sulfur content by beneficiation. Geological Society of India, 2013 High-sulfur Tertiary Coal nationallicence Pyrite nationallicence Mineral matter nationallicence Jaintia Hills nationallicence Meghalaya nationallicence Journal of the Geological Society of India Springer-Verlag 81/2(2013-02-01), 203-214 0016-7622 81:2<203 2013 81 12594 https://doi.org/10.1007/s12594-013-0023-9 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s12594-013-0023-9 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Nayak Bibhuranjan CSIR National Metallurgical Laboratory, 831 007, Jamshedpur, India aut NATIONALLICENCE 773 0- Journal of the Geological Society of India Springer-Verlag 81/2(2013-02-01), 203-214 0016-7622 81:2<203 2013 81 12594 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer