About two thousand years ago, different American Indian groups throughout eastern North America began using a similar set of beliefs, practices, and symbolism. Two trademarks of this culture were the construction of earthworks, often built in geometric patterns, and the manufacture of finely crafted objects made of exotic materials such as copper, mica, and marine shell gathered from distant lands. Although clues have been found, the true reason distinct groups over a large geographic area decided to engage in very similar behavior is unknown. Today, the name these groups used for themselves is also unknown. The term "Hopewell culture" refers to this range of shared beliefs, practices, and symbolism, which flourished from about 100 B.C. to 90 A.D. Archeologists derived the term from the man who owned the Hopewell Mound Group site in the late 1800s. Artifacts found there include a copper face made from copper acquired from the Lake Superior region, as well as a mica hand and partial human figure that might have been attached to clothing for ornamentation or used as ceremonial insignia.