Credit: The State Museum of Pennsylvania
Jasper, a form of quartz that contains iron minerals, occurs in a variety of colors. The amount of iron present and chemical alterations that affected the stone during formation can produce jasper that is yellow (butterscotch), red, green, or black. Native peoples throughout eastern North America heat-treated stone to improve its workability and gain greater control over the removal of flakes during the tool manufacturing process, so it is not uncommon to find a yellow jasper tool or flake that has a red tip or edge produced by heat treatment.
