Moganite

Moganite is an oxide mineral with the chemical formula SiO2 (silicon dioxide) that was discovered in 1984. It crystallises in the monoclinic crystal system. Moganite is considered a polymorph of quartz: it has the same chemical composition as quartz, but a different crystal structure. Moganite is an oxide mineral with the chemical formula SiO2 (silicon dioxide) that was discovered in 1984. It crystallises in the monoclinic crystal system. Moganite is considered a polymorph of quartz: it has the same chemical composition as quartz, but a different crystal structure. In 1994, the International Mineralogical Association (IMA) had disapproved it as being a separate mineral because it was not clearly distinguishable from quartz. It has only recently (1999) been approved as a valid mineral by the CNMNC, the Commission on New Minerals, Nomenclature and Classification (part of the IMA).Its IMA number is ( CNMMN，NO. 99－035) This mineral has been mainly found in dry locales such as Gran Canaria and Lake Magadi. It has been reported from a variety of locations in Europe, India and the United States. It was named for the municipality of Mogán on Gran Canaria. Physically, it has a hardness of about 6, a dull luster and appears as a transparent gray in color. The main infrared spectroscopy(IR) differences between moganite and α-quartz occur in the wavenumber region below 650 cm–1. Above this wavenumber, the frequencies of Si-O stretching vibrations of moganite are almost identical to those of quartz. Additional moganite bands were recorded near 165,207, 296, 343, 419, 576, and 612 cm–1. Synchrotron X-ray powder diffraction data for the silica mineral moganite from 100 K to 1354 K has revealed a reversible phase transition from space group I2/a to Imab at approximately 570 K. The in situ Fourier transform infrared spectroscopy show that while the thermal responses of H2O and OH in moganite display similarities to agate, the spectra are not completely identical. Absorptions in the O-H stretching region reveal that dehydration and dehydroxylation is a multi-stage process. Although hydrogen loss starts below 400–500 K, hydrous species may well remain in moganite even at 1060 K.