Chemical Formula: FeO(OH)

Chemical Name: Iron Oxyhydroxide

Mineral Class: Oxide

Mineral Notes: Goethite is derived by weathering from iron-beraring primary sulphide ores. It has a rich variety of crystal habits including tablets, scales, needles, radial and concentric aggregates. It is typically brown or black, but often gives a distinctive yellow streak, distingusihing it from other iron minerals which give a red colouration.

Description: Multi-faced crystals of Goethite replacing earlier Pyrite. There is considerable twinning. The specimen has an attractive earthy-brown colour and a strong metallic appearance.

Location: Blaengwynlais Quarry, Bwlch-y-cwm, Cardiff, Wales.