This piece of amber weighing 50.4kg, the world's largest, belongs to a Singapore businessman who wants to be known only as Mr Joseph. Formed in the Miocene era more than 15 million years ago, it was found early this year in a coal mine in Sumatra, Indonesia. This piece of amber reflects blue light under an ultraviolet light source (torch on right), and reddish-brown light under a daylight light source (torch on left). The owner would reveal only that the piece of amber cost him a six-figure sum in Singapore dollars more