Ferroan dolomite is a nebulous term that is applied to dolomite that has an iron content. Dylife mine, Central Wales Orefield. An off white aggregate with typical curved faces on the exposed fracture surface. The host rock on which it is deposited is a brecciated light coloured sandstone. Layering observed in the Dolomite indicates that this is a vein fragment.
Siderite, Iron carbonate, FeCO3. Ystrad Meurig quarry, Ysbyty Ystwyth, west Wales. A saddle shaped aggregate, cream in colour. No crystals are found on this specimen, but rhombohedral cleavage is apparent on the fractured surface.
Goethite, FeO(OH). Aberdaunant mine, Central Wales Orefield. Two, very thin deposits of goethite on a piece of host rock. The first deposit is pisolitic in nature, and is overlain by the second deposit which is in the form of an encrustation. The encrustation is removed here and there exposing the pisolitic first deposit.
Haematite(Hematite),Iron oxide, FeO2. Aberdaunant mine, Central Wales Orefield. The host rock appears to be brecciated sandstone. The Haematite, which is deposited on the surface is botryoidal in nature, albeit on a very small scale, and there are a few areas of iridescence, gold and silver in appearance. Also on the specimen is a small area encrusted with numerous very small brown crystals of quartz.
Baryte, Barium sulphate, BaSO4. Pen y Clun mine, Central Wales Orefield. Cream coloured massive baryte composed of compacted bladed crystals in random directions. A few bladed crystals are apparent and well defined in a vugh, indicating the nature of the crystals which make up the specimen as a whole.