The glass is often a uniform black to dark gray color and sometimes exhibits distinct black and dark gray banding. Surface luster varies from vitreous to earthy with a smooth to matte surface texture. Light transmittance qualities range from transparent to opaque. Prehistoric use of the obsidian appears to be restricted to a limited geographic area - with the exception of only two characterized artifacts correlated with the Butte Creek source have been identified (at 35-MA-141 and 35-CL-148 in the Willamette Valley), all artifacts from the Butte Creek source have been found at a single archaeological site alongside Butte Creek (Skinner 1999).