Quartz,SiO2. Bryn y Rafr mine, west Wales. There is nothing unusual or spectacular about this specimen. I have included it simply because it is part of my collection. This is a vugh of minute dark coloured druzy quartz crystals no more than a quarter of a millimetre in size. There is a small amount of lighter coloured quartz around the edges of the vugh.
Quartz, SiO2. Bryn y Rafr mine, west Wales. The two smaller specimens are skeletal in appearance, because the mineral which once occupied the cavities has weathered out. There are remnants of marcasite in a few places, and in the upper specimen there are numerous small cavities where impressions of the weathered mineral are well defined. The larger specimen is an example of crystal growth outwards from the two walls of a crevice or vein and meeting in the centre.
Quartz, SiO2. Van mine, Central Wales Orefield. These specimens were picked up many years ago, before "landscaping" removed all traces of mine waste. Today it would be almost impossible to find any mineral specimens from what was the largest mine in central Wales. The crystals are prismatic and of the milky quartz variety. The specimen with then larger and less distinct crystals has a slight surface discolouration due to iron staining.
Dolomite,CaMg(CO3)2. Bryntail mine, Central Wales Orefield. It is unusual to find such a well formed specimen of dolomite in the Central Wales Orefield. It is more usual to find ferroan dolomite. The specimen has a very uniform construction and the curved surface and rhombohedral habit is very obvious. The colour is greyish white and there is no sign of brown or other colours in this and other similar specimens found on the mine spoil heaps.
Chalcopyrite,Copper,iron sulphide.CuFeS2. Geufron mine, Central Wales Orefield. A nugget of massive chalcopyrite with a fractured face displaying the usual pale yellow colour. The rest of surface of the specimen has weathered and taken on the green colour of copper exposed to air. The chalcopyrite does not have any discernible crystals and is intermixed with a minor amount of quartz and very small pieces of host rock.