Maltildite mineral crystals, coloured scanning electron micrograph (SEM). This mineral contains the elements bismuth, silver and sulphur, and has the formula AgBiS2. Matildite was first discovered in the Matilda mine near Morococha in Peru, and is named after the mine. This sample is from the Clara Mine, in the Oberwolfach district, in the Black Forest, Germany. This mine is famed for the large number of minerals (more than 375) found here, some of which are very rare. Magnification: x265 when printed at 10 centimetres across.