Last week I gave you this rough and ready mystery object to identify:

I thought it might be a bit of a challenge as it had originally been misidentified as a piece of elephant tusk by someone in the museum, many years ago, so it was obviously not a straight-forward identification.

One of the key identifying characteristics of ivory are the Schreger lines, as pointed out by Carlos and rachel. These lines are an optical effect caused by light interacting with the dentinal tubules that provide the structure of the tusk:

Tusk section showing Schreger lines

However, these lines aren’t always visible and it will depend on the angle of the cut of the tusk and the angle and intensity of the light.

Another factor to keep in mind is the nature of the material. If you look at a cut section of elephant tusk you note that you get clean edges, because the tusk is quite hard and keeps its structure when cut. It can also show faint growth rings, radiating from the pulp cavity (nearer the tip the cavity is filled in):

Section of elephant tusk showing clean edges

Instead, the mystery object has a very rounded edge and no clear structure. This suggests to me that it’s horn that has been treated with heat to mould it into shape (keratin that makes horn and hair has thermoplastic properties, which is why hair straighteners work).

So what this mystery object appears to be is a piece of bovine horn – probably cow – that has been melted and shaped at one end to form a cup. The superficial similarity to elephant tusk may or may not have been accidental, after all, elephant ivory is a much sought after material.