where a trade network covered most of the Eastern Woodlands. Throughout the Southeast and north of the Ohio River, burial mounds of important people were very elaborate and contained a variety of mortuary gifts, many of which were not local. Among the traded materials were copper from the Lake Superior deposits; silver from Lake Superior and especially Ontario; galena from Missouri and Illinois; mica from the southern Appalachians; chert from various places including Ohio, Indiana, and Illinois; pipestone from Ohio and Illinois; alligator teeth from the lower Mississippi Valley eastward to Florida; marine shells, especially whelks, from the south Atlantic and Gulf coasts; Knife River chalcedony from North Dakota; and obsidian from Yellowstone in Wyoming. The most archaeologically certifiable sites of burial during this time were in Illinois and Ohio. These have come to be known as the Hopewell tradition. Due to the similarity of earthworks and burial goods, researchers assume a common body of religious practice and cultural interaction existed throughout the entire region (referred to as the "Hopewellian Interaction Sphere"). Such similarities could also be the result of reciprocal trade, obligations, or both between local clans that controlled specific territories. Access to food or resources outside a clan's territory would be made possible through formal agreements with neighbors. Clan heads would be buried along with goods received from their trading partners to symbolize the relationships they had established. Under this scenario, permanent settlements would be likely to develop, leading to increased agricultural production and a population increase. Ceramics during this time were thinner and better quality than earlier times. Examples show pottery also was more decorated than Early Woodland. One style was the Trempealeau phase, which could have been seen by the Hopewell in Indiana. This type included a round body, and lines of decoration with cross-etching on rim. The Havana style found in Illinois had a decorated neck. One of the major tools unique to this era was Snyders Points. These were quite large and corner-notched. They were made by soft-hammering percussion, and finished by pressure flaking. Although many of the Middle Woodland cultures are called "Hopewellian", and groups shared ceremonial practices, archeologists have identified the development of distinctly separate cultures during the Middle Woodland period. Examples include the Armstrong culture, Copena culture, Crab Orchard culture, Fourche Maline culture, the Goodall Focus, the Havana Hopewell culture, the Kansas City Hopewell, the Marksville culture, and the Swift Creek