Eulysite - fayalite-hedenbergite-magnetite rock Carr Brae, Dornie, Skye (NG901 246)

PPL: A eulysite is a metamorphic rock consisting of Fe and Mn bearing silicates such as the pyroxenes hedenbergite and hypersthene, the olivine fayalite and the garnets almandine and spessartine. The greenish brown minerals seen above are the pyroxenes, the garnets and olivines are pale yellow brown and distinguishable under crossed polars in so far as the former are isotropic under crossed polars. The opaques are magnetite.

Hand specimen: (NB: The hand specimen does not conform to the thin section photo's). The bright areas are magnetite (Fe3O4); when the hand specimen was held over a compass, the needle was considerably deflected. Red-brown colours, seen mainly towards the right are garnets. The rock is deemed to be of Precambrian (Lewisian) age.
It was not until the 1930's that this type of ultrabasic metamorphic rock was recognised in Britain. Previous examples were mainly from Scandinavia.

On the map below, 411 refers to locality of above specimen: 399 is locality of the pyroxenite.    

The same photo as the above, but in XPL.

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