Ilmenite, sphene, haematite and epidote. Glen Gairn, Scotland




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125µm


A diorite contains haemoilmenite (centre) that comprises an ilmenite host (brown) with very fine haematite (white) exsolution discs along (0001) of the host ilmenite. Later haematite (white, centre right) has overgrown the haemoilmenite but lies within sphene (light grey, centre), which rims the primary iron-titanium oxides. A subhedral crystal of pyrite (pale yellow-white, bottom left) is associated with epidote (medium grey, bottom left), which has a slightly lower reflectance than sphene, although the difference is difficult to see. Elsewhere, fine-grained epidote lies along the cleavage of the chloritized biotite host (top right). Epidote is more easily identified in transmitted light.


Polished thin section, plane polarized light, x 160, oil



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