Vein breccia.

Vein breccia.

This specimen of cut and polished vein breccia is interesting for two reasons. The first point of interest is that the breccia/wall rock boundary is very prominent. Next, there are very angular shards of the same wall rock in the breccia, demonstrating the power of hydraulic action. The cream coloured mineral is a dolomitic carbonate, and there are areas of  a bronze coloured mineral which is sphalerite. The inset picture shows the unpolished rear of the specimen, and it was collected from the Cwmrheidol mine, West wales, by John Philips in the 1960s-70s