Hydraulic brecciation.

Hydraulic brecciation.

Cafartha mine, Staylittle, Central Wales ore field. This pretty little specimen is a mix of host rock, with precipitated quartz, some of which is druzy and lining small cavities. There are also very minor amounts of galena on the surface. Brecciation is the result of inwardly exploding walls of deep fractures when there is a sudden decrease of pressure causing shards of wall rock to be injected into the hot mineral rich fluids which are circulating through the fracture.