a well-known gem of pure green color, somewhat harder than quartz. It is a variety of beryl. Its color is due to the presence of chromium. Its natural form is either rounded or that of a short, six-sided prism. It is one of the softest of the precious stones, but is not acted upon by acids. Emeralds of large size and free from flaws are rare; the largest on record is said to have been possessed by the inhabitants of the valley of Manta, in Peru, when the Spaniards first arrived there. It was as big as an ostrich egg and was worshiped as the mother of emeralds. The ancients, who valued emeralds, especially for engraving, are said to have procured them from Ethiopia and Egypt. The finest are now obtained from Colombia. The Oriental emerald is a variety of the ruby, of a green color, and is an extremely rare gem. Emeralds have been found in North Carolina.