Moganite

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Not to be confused with Morganite (gem).
Moganite
Specific gravity
2.52 – 2.58
Optical propertiesBiaxial
Refractive indexnα = 1.524
nγ = 1.531
References[2][3][4]

Moganite is an oxide mineral with the chemical formula SiO2 (silicon dioxide) that was discovered in 1976. It was initially described as a new form of silica from specimens found in the Barranco de Medio Almud, in the municipality of Mogán on the island of Gran Canaria, in the Canary Islands (Spain),[5] receiving in a later work the name derived from this locality.[6] In 1994 the International Mineralogical Association decided to disapprove it as a valid mineral, since it was considered indistinguishable from quartz.[7] Subsequent studies allowed the IMA to rectify it in 1999, accepting it as a mineral species.[8] It has the same chemical composition as quartz, but a different crystal structure.[4]

This mineral has been mainly found in dry locales such as Gran Canaria and

Mohs hardness
of about 6, a dull luster and appears as a semitransparent gray in color.

Structural information

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.[10]

Structural phase transition

X-ray powder diffraction data for moganite from 100 to 1,354 K (−173 to 1,081 °C) has revealed a reversible phase transition from space group I2/a to Imab at approximately 570 K (297 °C).[11]
The in-situ
dehydroxylation is a multistage process. Although hydrogen loss starts below 400–500 K (127–227 °C), hydrous species may well remain in moganite even at 1,060 K (790 °C).[12]

References

  1. S2CID 235729616
    .
  2. ^ "Mineralienatlas Lexicon – Mogánite". Mineralienatlas. Retrieved 13 August 2023.
  3. ^ a b Ralph, Jolyon; Ralph, Ida (2007). "Moganite: Moganite Mineral Information and Data". MinDat. Retrieved 1 August 2007.
  4. ^ a b "Webmineral data".
  5. ^ Flörque, O.W.; Jones, J.B.; Schmincke, H.U. (1976). "A new microcrystalline silica from Gran Canaria". Zeitschrift für Kristallographie. 143: 156–165.
  6. ^ Flörque, O.W.; Flörque, U.; Giese, U. (1984). "Moganite, a new microcristaline silica-mineral". Neues Jahrbuch fur Mineralogie (Abhandlungen). 149: 325–336.
  7. ^ Origlieri, M., 1994. "Moganite: a New Mineral – Not!" Lithosphere. Aug. 2007 http://geopress.rbnet.net/moganite.htm
  8. doi:10.2113/gscanmin.38.1.245
    .
  9. S2CID 32497622
    .
  10. S2CID 56255006
    .
  11. S2CID 6093768
    .
  12. doi:10.1127/0935-1221/2011/0023-2165
    .
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