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Silicon Spinel

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Formula:
2Al2O3 · 3SiO2 or possibly γ-Al2O3
may also be formulated as Al4Si3O12
A phase (synthetic) known to be formed due to thermal transformation of kaolinite adn illite, e.g. in coal combustion. May be formed from thermal destruction of 'meta-kaolinite' or 'meta-illite' at 900oC. At 950oC it transforms to 'pseudomullite'.

In the presence of CaO it transforms to anorthite and 'pseudomullite', at 850-1100oC. When the content of available CaO is larger, the product (at 950-1100oC) is gehlenite. It may also be a precursor to esseneite, if considerable amount of Fe2O3, CaO, and SiO2 is present in the environment and the temperature is 950-1100oC (Querol et al., 1994).

It is quite likely, that this phase corresponds to γ-alumina. According to Sun et al. (2006), the spinel-type structure is attributable to this form of Al2O3 instead of non-spinel ones. Also, Ward (2002) reports (cites) that 'meta-kaolinite' transforms to γ-alumina, mullite and cristobalite at 950-1000oC, which somehow fits to the aforementioned processes.

It seems possible, that this phase exists in natural pyrometamorphic zones.


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Classification of Silicon SpinelHide

Notes:
Unnamed (probably invalid)

Pronounciation of Silicon SpinelHide

Pronounciation:
PlayRecorded byCountry
Jolyon & Katya RalphUnited Kingdom

Chemical Properties of Silicon SpinelHide

Formula:
2Al2O3 · 3SiO2 or possibly γ-Al2O3

may also be formulated as Al4Si3O12

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Silicon SpinelHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Querol, X., Fernandez Turiel, J.L., Lopez Soler, A. (1994): The behaviour of mineral matter during combustion of Spanish subbituminous and brown coals. Mineralogical Magazine: 58: 119-133
Ward, C.R. (2002): Analysis and significance of mineral matter in coal seams. International Journal of Coal Geology: 50: 135-168
Sun, M., Nelson, A.E., Adjaye, J. (2006): Examination of spinel and nonspinel structural models for gamma-Al2O3 by DFT and rietveld refinement simulations. The Journal of Physical Chemistry B: 110(5): 2310-2317

Internet Links for Silicon SpinelHide

Localities for Silicon SpinelHide

ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Poland
 
  • Silesia
    • Upper Silesian Coal Basin
      • Rybnik Coal Area
        • Rybnik
          • Jankowice
Ł. Kruszewski EPMA data
Mineral and/or Locality  
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