This image of a fossilised ammonite from Alberta, Canada, hasn't been altered.

The mollusc fossil's fluorescent colours occurred naturally when its original shell substance turned to a mineral called aragonite.

The conditions which produce the colours are unique to the Bearpaw formation in Southern Alberta. 

This fossil is so unique that it is to be auctioned at Christies, on April 7.

Two ammonites will be up for sale. The smaller one (in the photo) has a book price of $68,000. The larger of the two is expected to sell for over £100,000.

Less wealthy collectors can find cheaper, smaller and slightly less colourful specimens online.

But none will be as valuable to collectors, or have the projected appreciation levels, of the Alberta specimen.