The Hopewell created some of the finest craftwork and artwork of the Americas. Most of their works had some religious significance, and their graves were filled with necklaces, ornate carvings made from bone or wood, decorated ceremonial pottery, ear plugs, and pendants. Some graves were lined with woven mats, mica (a mineral consisting of thin glassy sheets), or stones. The Hopewell produced artwork in a greater variety and with more exotic materials than their predecessors the Adena. Grizzly bear teeth, fresh water pearls, sea shells, sharks' teeth, copper, and small quantities of silver were crafted as elegant pieces. The Hopewell artisans were expert carvers of pipestone, and many of the mortuary mounds are full of exquisitely carved statues and pipes.