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Agate Basin This type is named after points found at the Agate Basin site complex in eastern Wyoming. Excavations at this well-stratified site produced multiple point types, including a Folsom–Agate Basin–Hell Gap sequence, each associated with discrete beds of extinct bison bones. The main bison bone bed (Area II) was situated 20 to 30 centimeters above a Folsom level and produced forty-six complete and broken Agate Basin points.

Other Possible Names or Related Points: Angostura, long or oblique Yuma.

Age: 10,500 to 10,000 B.P. Charcoal from the Agate Basin component at Area II produced a radiocarbon date of 10,430 + 570 B.P.

Distribution: This type is widespread on the Plains, extending east as far as Ohio and Lake Michigan, and is found on both sides of the upper Mississippi River. East of the Mississippi River, this type is most concentrated in western Illinois and southern Wisconsin.

Description: Medium to large in size, Agate Basin lanceolates were used as spear tips and knifes. They are widest at their midsection with convex edges that narrow to the base. Their blades are often carefully flaked in a collateral pattern where the horizontal flake scars meet at a central ridge. The bases are usually straight but may be slightly concave or convex. The lower edges are normally ground heavily, and sometimes the grinding extends nearly 7 centimeters above the base. Short Agate Basins are often nubs of larger points that were resharpened until the blade was nearly gone, and these may be confused with Hell Gap points. On these points all but the very tip is ground.

Length: 6–15 cm/2.5–6 in. Width: 2.5­–4 cm/1–1.5 in.

Material: These points are usually made from regionally available cherts such as Galena, Moline, and Burlington, or silicified sandstone. Numerous examples made of Hixton silicified sandstone and nonglossy tan Cochrane chert are known from western Wisconsin. A few Agate Basin points made from exotic flint have also been reported for this region. For example, Hill reports the base of an obsidian specimen from Silver Mound, and Knife River flint specimens are also known from the Upper Mississippi Valley. In addition, a few examples made from jasper taconite and Silurian II chert from Lake Superior and Green Bay, respectively, are known to have come from this region.