Fossilised Shark Tooth (Approximately 100 Million Years Old) on Black Cord Necklace Genuine Fossilised Shark Tooth (Approximately 100 Million Years Old) on Black Cord Necklace. The necklace measures approximately 46 cm. The Shark tooth measures approximately 2 - 2.5 cm in length. Please note that the size, shape and coloring of the tooth that you receive may be different from the picture as no two are the same.