Q: Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
Context: The Nimrud ivories are carved ivory plaques and figures dating from the 9th to the 7th centuries BC that were excavated from the Assyrian city of Nimrud (in modern Ninawa in Iraq) during the 19th and 20th centuries.
Question: What is the surface of Nimrud ivories made of?
A:
ivory