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.