Virtual Atlas of Opaque and Ore Minerals
Sphalerite, bournonite and galena. Navan, Ireland
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