Comparative mineralogical study of thermally-altered coal-dump waste, natural rocks and the products of laboratory heating experiments

Columnar structures in pyrometamorphic rocks associated with coal-bearing spoil-heaps burned by self-ignition, La Ricamarie, Loire, France

“…Anorthite is actually a ternary feldspar containing some K2O. The indialite (polymorph of cordierite) compositions compare well with those given by Gawęda et al (2013) and Ciesielczuk et al (2015); indialites invariably contain thin needles as inclusions, too thin to be analyzed. Hematite contains some TiO2; hercynite spinel is too small for analysis, but it could be the carrier phase of Zn in sample PAC3.…”

“…Main rock forming minerals are SiO2 phases (see below), anorthite, indialite, mullite, hematite, magnetite, spinel (cf. Ciesielczuk et al 2015, compare with Ciesielczuk et al 2014. Neither corundum nor fayalite were detected (this mineral has been found in some iron-rich slags and in other Fe-rich melted combustion metamorphic rocks elsewhere in the world, cf.…”

Self-Heating Coal Waste Fire Monitoring and Related Environmental Problems: Case Studies from Poland and Ukraine

“…Structures of mineral phases which are not stable at higher temperatures can be destroyed, and amorphous and metastable phases formed. Highest temperatures can lead to melting and paralava formation (Ciesielczuk et al, 2014(Ciesielczuk et al, , 2015Pierwoła et al, 2018). Overburned parts of the dumps dominate in combusted phases as cristobalite-tridymite, celsian, anorthite, cordierite, indialite, mullite, olivine, augite, spinel group, hematite, and glass.…”

Genesis, evolution and economic significance of the northen and the eastern parts of Karapinar-Ayranci coal deposit

“…Akermanite is a typical Ca-Mg silicate in studied ash residues; however, the akermanite and gehlenite XRD patterns are similar and therefore, their contents may not be determined accurately. Forsterite is rarely reported from fly and bottom ashes (Steenari et al, 1998); however, forsterite and other Mg-Fe olivine minerals are included in burned coal-bearing soil heaps as result of silicate melt inclusion (Sokol et al, 1998;Ciesielczuk et al, 2014).…”

“…The formation of these Ca-Mg silicate minerals can be explained through similar ways. Even though forsterite is generally formed at high temperature (≥ 1200°C), forsteritic olivine can start developing at lower temperatures during thermal alteration of coal (Ciesielczuk et al, 2014). Moreover, magnesium is mostly organically bound in low-rank coals and as such is also determined in macerals by SEM analysis (see Chapter 6.6).…”