Mineral Database

Mineral Database
Mineralogy of Wales

Ottrélite

Crystal System: Monoclinic
Formula: (Mn,Fe,Mg)Al2O(SiO4)(OH)2
Status of Occurrence: Discredited Occurrence
Distribution: See individual species entries for details
Chemical Composition: Manganese iron magnesium aluminium silicate hydroxide
Method(s) of Verification:
Chemical Group:
  • Silicates
Geological Context:
  • Metamorphic : medium-grade
  • Metamorphic : low-grade
Introduction: ottrélite is a manganese-rich chloritoid. The name is applied to compositions where the manganese, iron and magnesium site is occupied by 60% manganese. Like chloritoid, ottrélite is found in low- and medium-grade metamorphic rocks.
Occurrence in Wales: the only record of ottrélite from Wales is from ‘Snowdon’ by Hall (1868); similar minerals in this district have subsequently been shown to be chloritoid, although they do contain up to 8.06 weight % manganese oxide (MnO). See reference to Brearley (1988) in chloritoid entry.
Key Localities:
There are no key localities for this specimen.
References:
  • Brearley, A.J., 1988 Chloritoid from low-grade pelitic rocks in North Wales.  Mineralogical Magazine, 52, 394-396.
  • Hall, T.M., 1868 The Mineralogists' Directory.  London, 168pp.