Photo -- See Caption Below

Thumb Scraper
Certain tasks demanded the use of particular tools. This stone tool was commonly used for detailed hide preparation and processing. It is often called a “thumb scraper” in reference to its small thumb-like size [coin included to show size]. It was manufactured using a unifacial pressure flaking technique from a larger chalcedony percussion flake. Chalcedony is a cryptocrystalline silica stone type locally available throughout Nez Perce Country.
Silica. L 3.5, W 3 cm.
Nez Perce National Historical Park, NEPE 3000