Crystal System: Triclinic
Status of Occurrence: Unconfirmed Occurrence
Chemical Composition: Magnesium aluminium silicate hydroxide
Chemical Formula: Mg2Al(Si,Al)2O5(OH)4
Method(s) of Verification: Cefn Coed Colliery – X-ray diffraction (Natural History Museum, No. x2724) suggests either 'amesite or chrysotile'.
Introduction: amesite belongs to the kaolinite-serpentinite family of minerals and is generally found in magnesium-rich aluminium bearing rocks, such as serpentinite.
Occurrence in Wales: there is only one reported occurrence of amesite from Wales. This is based on X-ray analysis of material from a colliery in South Wales, which produced a result,'amesite or chrysotile'. Until further analyses are carried out this should be regarded as an unconfirmed species in Wales.
- Cefn Coed Colliery, Neath: amesite was reported from the Dulais Seam, Cefn Coed Colliery, on the basis of X-ray diffraction analysis. However, this analysis suggested 'amesite or chrysotile', therefore amesite has not been totally confirmed. This occurrence may seem unusual as the mudstones and sandstones of the Coal Measures sequence are not magnesium enriched. One explanation of this is that much iron became locked into pyrite during diagenesis and low-grade metamorphism, thus enriching the rock in magnesium relative to iron.
There are no references for this specimen.