Wampum consists of small cylindrical beads, often about 5-7 mm long and 1.5 mm wide. Historically these were made from purple and white shells, the purple coming from the edge of the quahog clam (Mercenaria mercenaria), and the white from the columns of univalve whelks (Busycon).Wampum beads were manufactured by Algonquian-speaking peoples along the coast of New England, by Iroquois, and by white manufacturers (Dutch and British soldiers, for instance). Later they were made in specific factories in New Jersey and elsewhere, until the nineteenth century. In the early seventeenth century, the Dutch realized that wampum could be used as a currency in the inland fur trade with the Iroquois; they introduced the idea to the Pilgrims in Massachusetts in the 1620s.The Iroquoian- and Algonquian-speaking peoples used wampum for decoration and adornment. It was also used to make woven belts, with the two colours acting as mnemomic devices commemorating agreements and events important in politics, history and religion. This example has a design of three rectangles, suggesting an alliance of three groups in war, suggested by the use of purple.Before European contact, when metal tools became available, flat disc shaped beads were made. Metal drills enabled the creation of cylindrical beads. From the late eighteenth century these were replace by imitation glass wampum, probably made in Venice.