Ivory, at the tip of a complex issue for traveling orchestra members

It's a mere quarter of a gram of ivory -- about 1/100 of an ounce -- embedded at the bottom tip of many violin bows. But because it comes from the tusks of the African elephant, its presence -- often on the bow tips of viola, cello and bass players as well -- has become a major headache for U.S. orchestras and soloists leaving the country for tours overseas.