Hippopotamus comes from the Greek hippo meaning horse and potamos meaning river or rushing water but in Afrikaans it is seekoei meaning sea cow and the German word is Nilpferd meaning Nile horse! Strangely, the hippo’s large, curved lower canines are more like giant pig tusks than anything you would see in the mouth of a cow or horse.
If you can find a surface on an object that cuts across the tusk it is easy to tell from any other type of ivory because hippo canines are triangular in section. All the layers in the ivory follow the same triangular path around the discontinuity in the centre of the tusk, an angled dotted line called the angular tusk interstitial zone or commisure. Variations in the way the dentine is formed can produce a range of very different markings in the ivory but the way the concentric layers converge on the commisure and then sharply changing direction, is an unmistakeable feature of hippo canine ivory – unless it really is the tusk from a 5,000 lb pig!
In life, two sides of the tusk are covered in enamel, but this was often removed before carving because it is so white, hard and brittle compared to the ivory (dentine). The commisure can be very disfiguring in a worked object so it was often camouflaged by lines of decoration or the piece was cut so that the commisure was only obvious on the base or back of the carving.