Vesuvianite mineral sample. Also known as idocrase, this is a complex silicate mineral. It contains calcium, magnesium and iron, and well as fluoride. The crystals here are yellow-brown mixed with other minerals, but they can vary in colour. It is named for the place where it was first found, the volcano Mount Vesuvius. This sample is from Monte Somma, Italy, the ancient volcano whose caldera circles the current volcano of Vesuvius. It is 6 centimetres across.