Sphalerite, bournonite and galena. Navan, Ireland

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Sphalerite crystals display abundant light yellow to brown internal reflections and are cemented by bournonite, which shows its characteristic polysynthetic twinning on (110) 'parquet-twinning' (centre). Minor amounts of galena (lilac-white, bottom centre,) are intergrown with bournonite. The lilac-white colour of galena is due to the partial crossing of the polars.

Polished block, plane polarized light, x 160, oil

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