A hornstone variety with tiny white fossils in the matrix--you see the white specks, you know this was a layer (lense) form of Hornstone--it's not Illinois Cobden Flint, so the Harahey knapper found some 'other source', made the four-sided-knife from a flint slab he chose. Length is slightly under 3&3/8", pointed end to slightly dulled hand-hold on the flattened end--you can feel how they dulled the edges of the flat end slightly--it had to have cut into the users hand otherwise. Norman Reid found the piece, notated his provenance as Edwards County, Illinois, 1958--long time back, I was going into first grade when he found the piece, added it to his "Indian Hill Museum" in Bone Gap, Illinois. Width is 1&5/16", and as the title says--THIN; my caliper doesn't slide over 1/4"--excellent thinning of the preform the Mississippian Culture knapper fashioned. Give them credit, flintwork was as much art as labor. With some luck the pics will show the beveled edges Harahey Knives are known for--neat piece. Shipping is $8.00 with checks or M.O.s how I welcome payments--sorry, I do not use paypal-type services--Roy A.