Pyromorphite, Pb5(PO4)3Cl is lead chloride phosphate, a secondary lead mineral found in the oxidised zone of lead deposits. The hexagonal barrel shaped crystals may vary in appearance from stubby to elongated, and the colour is also variable, but usually a shade of green. The specimen is from Driggeth mine in Cumbria.
Haematite is an iron oxide, Fe2O3 This specimen is botryoidal in habit, a habit which is commonly referred to as " Kidney Ore ". Hematite is mined as the main ore of iron, and this specimen is from the Frizington iron mine in Cumbria.
Dolomite, CaMg(CO3)2 , and Quartz, SiO2, are featured in this rock from Penstrowed quarry, Newtown, central Wales. This specimen is very similar to another which was collected from a quarry at Cefn Coch, several miles away. Both quarries are in the Penstrowed Grits Fm, a mid Silurian sedimentary deposit. The rock has several vughs of quartz crystals, and dolomite crystals, both of which are very sharp and well formed.This specimen weighs about 30kg.and was kept in this state, because breaking it might have destroyed the minerals.
Castell mine, west Wales. This fine example of hydraulic brecciation is made up of host rock, quartz, and ferroan dolomite. The brecciation is the result of inwardly exploding walls in deep fractures. A sudden decrease of pressure causes shards of wall rock to be injected into the hot mineral rich fluids which are circulating through the fracture. Larger pieces of the ferroan dolomite can easily be found on the spoil heaps at this long abandoned mine. Along with quartz, the ferroan dolomite would be considered as one of the gangue minerals at the mine.
Sphalerite, (Zn,Fe)S. and Siderite, FeCO3. Castell mine, west Wales. The bulk of the specimen is massive siderite with just the odd observable crystal. The sphalerite is randomly distributed in small pockets, and in a few places the very deep red colour of sphalerite can be seen.