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Silicon Spinel

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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

Unnamed (probably invalid)

Pronounciation of Silicon SpinelHide

PlayRecorded byCountry
Jolyon & Katya RalphUnited Kingdom

Chemical Properties of Silicon SpinelHide

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.
  • Silesia
    • Upper Silesian Coal Basin
      • Rybnik Coal Area
        • Rybnik
          • Jankowice
Ł. Kruszewski EPMA data
Mineral and/or Locality  
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