Jet is actually a fossilised wood rather than a stone, formed around 180 million years ago by Araucaria tree. The most famous Jet comes from the UK, in Whitby, and was made popular by the Victorians. Whitby Jet is where the expression 'jet black' originates from, due to its intense deep black. Jet has been mined since 1400 BC, for use in jewellery and as a protection stone. Jet can also become electrically charged, in a similar way to amber, by rubbing it with a soft cloth.