'Ivory' in the Bible

Then the king made a great ivory seat, plated with the best gold.

For the king had Tarshish-ships at sea with the ships of Hiram; once every three years the Tarshish-ships came with gold and silver and ivory and monkeys and peacocks.

Now the rest of the acts of Ahab, and all he did, and his ivory house, and all the towns of which he was the builder, are they not recorded in the book of the history of the kings of Israel?