This object is a mineral composed of willemite, calcite, hendricksite and andradite from the Franklin Mines in Franklin New Jersey.

Many minerals are popular for their colour. Their textures can vary from the smooth glassy surface of quartz crystals to the slippery feel of soapstone. Some minerals form peculiar and interesting shapes.

This one spectacularly glows red and green under short-wave UV light: a phenomenon known as fluorescence. The photographs above show this transformation.

Fluorescence is a property exhibited only by certain types of minerals. These often look dull in normal light but when put under ultraviolet light they change colour. This happens because the UV light's energy is absorbed and then given out as coloured light.

You can see this object, other minerals like it and find out more about other types of rocks on display in the new Elements gallery.