Moganite - A new microcrystalline Silica-Mineral
Flörke, O. W.; Flörke, U.; Giese, U.
Neues Jahrbuch für Mineralogie - Abhandlungen Band 149 Heft 3 (1984), p. 325 - 336
5 références bibliographiques
publié: Aug 2, 1984
DOI: 10.1127/njma/149/1984/325
ArtNo. ESP154014903006, Prix: 29.00 €
Abstract
Moganite (formerly SiO2-G) is a new microcrystalline silica mineral closely associated with the family of microcrystalline quartz species. It occurs in ignimbrite flows near Mogan, S-Gran Canaria. The properties: Colour gray, luster like chalcedony; ao = 4.934 Å, bo =10.761, co = 8.533, β = 92.29°; n ≈ 1.52; ρ ≈ 2.55g/cm3; thermal expansion between 20 to 400 °C is comparable with chalcedony, above 400 °C it decreases, reaching zero at about 700 °C. The microstructure consists of lepidospheres with optical length-slow character. The concentration of non-volatile impurities is about 0.1 wt%, the volatile impurities are ca. 2 wt% H2O, 0.5 wt% CO2 and minor amounts of CO and F. The ratio of concentrations of silanole-group-water to molecular water is about 1.5. According to X-ray and electron diffraction data G. Miehe has developed as a tentative structural model a three dimensional tetrahedral framework, consisting of alternatingly stacked left- and right-handed lattice slices, which are similar to 1011-quartz-lattice slices.
Mots-clefs
New mineral • silica mineral • moganite • microstructure • chemical composition • water bonding • crystal structure