 The obsidian is most abundant at the base of the cliff and slowly tapers off to larger concentrations of pumice at the top.Obsidian from this site was first quarried here about 12,000 years ago.Early natives of North America placed a high value on the obsidian that came from this cliff as well as other similar obsidian deposits in the area because numerous tools could be fashioned from obsidian—most popularly, knives, spear/arrow tips, and other sharp-edged objects.