Dana, they range from a couple inches long to over a foot. Some are heavily serrated, some not. Some are lightly fluted, some aren't.Most classic Midwestern ones are made from Burlington, Pitkin, or other cherts. The Southeastern variants (Hardaway-Dalton, Greenbrier-Dalton, etc. ) were made from rhyolite, Coastal Plains Chert, even from quartzite. Here's some good examples from the Lithic Casting Labs site.
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