The results of this and an earlier study (LBL 13247) lead to the conclusion that nearly all of the artifactual material studied so far may derive from two sources, one designated QuiscatolaYanaurco, after two mountain peaks close to the volcano Antisana, the other designated Mullumica. There is evidence that Mullumica, considered the most important obsidian source in northern Ecuador, may be a source with variable composition owing to mixing of magmatic flows of different composition prior to or during eruption. See 18-1021. -- AATA