Crystal System: Monoclinic
Status of Occurrence: Discredited Occurrence
Distribution: See individual species entries for details
Chemical Composition: Manganese iron magnesium aluminium silicate hydroxide
Chemical Formula: (Mn,Fe,Mg)Al2O(SiO4)(OH)2
Method(s) of Verification:
- 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.
There are no key localities for this specimen.
- 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.