Sample of Bismuth.
© Science Museum / Science & Society Picture Library
Bismuth is a hard, brittle metallic element. It has the highest atomic number of all the stable elements and occurs in ores and occasionally as a free metal. It is a poor conductor of heat and electricity and is used in alloys of low melting point. Inside this piece of bismuth are intricate 'nests' of crystal boxes, formed as the metal slowly solidified. The outer part of the bismuth cooled quickly and formed only microscopic crystals.