Short answers, pulled from the story.
Ivory carving is the carving of animal tooth or tusk, generally using sharp cutting tools applied either mechanically or manually. While elephant tusks are the most common source, ivory can also come from walrus, mammoth, hippopotamus, and sperm whale teeth, among other species with large tusks or teeth.
Ivory has no bullion value and cannot easily be recycled or remelted, so carved pieces were kept rather than broken down for raw material. Unlike precious metals, a thin ivory panel could not be repurposed, giving ivory objects a much higher survival rate than equivalent works in gold or silver.
The Venus of Brassempouy, considered arguably the earliest real likeness of a human face, was carved from mammoth ivory and is approximately 25,000 years old.
Paris became the dominant centre of ivory carving from the 13th century onward, operating at virtually industrial scale and exporting pieces across Europe. The city's prominence grew as African elephant ivory became more widely available in Europe from that period.
The Umayyad ivory caskets were intricately carved containers likely produced in the workshops of Madinat al-Zahra, a palace in Cordoba, Spain. They featured hunting scenes, floral patterns, geometrical designs, and Kufic script, and were made for elite political and religious figures of the Umayyad caliphate.
CITES enacted the ban on international trade in ivory in January 1990. In the United States, the Interior Department's Fish and Wildlife Service announced a further ban on trade in elephant ivory within the country in February 2014, prohibiting imports and, with narrow exceptions, exports and resales.