Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more . CNN  —  Hundreds of obsidian artifacts have revealed where the Aztecs acquired the volcanic glass they used for tools, ornamental pieces or religious objects centuries ago — and their vast trade networks included their rivals. A new study of the 788 pieces is the largest sample of obsidian artifacts ever analyzed for Tenochtitlán, which served as the