Calcite, calcium carbonate, CaCO3. Nantiago mine, Central Wales Orefield. This particular specimen appears to be composed of myriads of very small rhombohedral crystals, many of which are arranged in regimented rows or columns. There are a few small vughs where the construction of the crystals can be better observed, albeit with the aid of a microscope. There are also several small well formed cubes of pyrite inside the vughs.
Sphalerite, Zinc sulphide, (Zn,Fe)S. Cwmbryno mine, west Wales. Sphalerite in brecciated rock. An aggregate of the zinc sulphide, with no well defined crystals. There is a coating of fine druzy quartz on one surface, and also some iron staining. This type of specimen is typical of many to be found on lead mine spoil heaps.
Quartz, SiO2, Eaglebrook mine, west Wales. A fine example of druzy quartz. Although druzy quartz is not uncommon and not of particular scientific interest, this specimen with its well formed stubby prismatic crystals proved to be too nice to leave on the spoil heaps.
Baryte, Barium sulphate, BaSO4. Bryntail mine, Nr Llanidloes, Central Wales Orefield. A few specimens recovered from the sorting platform at the remains of the mine. Notice the layered structure, which is not uncommon in specimens from this mine.
Haematite(Hematite), Iron oxide, Fe2O3, Dylife mine, Nr. Staylittle, Central Wales Orefield. This rather weighty specimen is obviously a small part of a much larger original formation. There are obvious signs of a radiating construction on the reverse. The surface texture is made of indistinct crystals, possibly the terminations of a radial growth. The specimen is non-magnetic, implying that there is no magnetite present.