Fossil ammonite, Madagascar. Sold individually.

These fossil ammonites from Madagascar show a natural iridescent outer layer.

Ammonites are extinct relatives of modern day nautiloids and squid. The largest known ammonite in the world would have been 8 1/2 feet (2.59 metres) across if it were complete.

Left: 5/8 inch (1.6 cm) wide, 7/16 inch (1.1 cm) deep, 1/2 inch (1.3 cm) tall.

Middle: 13/16 inch (2.0 cm) wide, 1/2 inch (1.3 cm) deep, 3/4 inch (1.9 cm) tall.

Right: 15/16 inch (2.4 cm) wide, 9/16 inch (1.4 cm) deep, 7/8 inch (2.2 cm) tall.