Contribution
Heating products of glauconitic materials
Slovenec, Dragutin; Popović, Stanko; Tadej, Neven
Neues Jahrbuch für Mineralogie - Abhandlungen Band 171 Heft 3 (1997), p. 323 - 339
39 références bibliographiques
publié: May 15, 1997
DOI: 10.1127/njma/171/1997/323
ArtNo. ESP154017103004, Prix: 29.00 €
Abstract
Four practically pure, mutually chemically different, glauconitic materials, as mixtures of glauconite and interstratified glauconites - smectites (having relatively small expandibility) were isolated from the Lower Miocene sandstones at several localities in Croatia. Glauconitic materials were successively heated for 3 hours at 980, 1080, 1180, and 1300 °C. The heat-treated samples were analysed by means of X-ray powder diffraction (identification, determination of the unit-cell parameter a of magnesioferrite and semiquantitative phase analysis). The amounts of FeO in samples were also determined. On the basis of the data obtained for the heat-treated samples and the data on the starting glauconitic materials (using the “wet” chemical analysis, infrared spectroscopy, differential thermal analysis and thermogravimetry, beside X-ray diffraction), the following conclusion was drawn: (1) after the destruction of the crystal structure of glauconite, the heating products at 980 °C were an amorphous fraction (glass) and magnesioferrite; (2) in the materials for which the content of Fe3+ was much bigger than that of AlVI, magnesioferrites were formed which were solid solutions of MgFe2O4, γ-Fe2O3 and Fe3O4; otherwise, in the material with a high amount of AlVI a magnesioferrite was formed which also contained Al; (3) the fraction of magnesioferrite gradually decreased as the temperature of heating increased to 1080 and 1180 °C, while hematite and enstatite were formed; (4) after heating at 1300 °C magnesioferrite was again the single crystalline phase, but containing a bigger amount of divalent iron and having a bigger unitcell parameter a than magnesioferrite formed at 980 °C.
Mots-clefs
Glauconite • glauconitic materials • heating products of glauconitic materials • magnesioferrite • hematite • enstatite