"mirrors of volcanic glass called obsidian"
Obsidian Mirror
Permission Granted by Copyright Owner for Use on Book DrumObsidian Mirror - Credit: Trustees of the British Museum

According to the British Museum, home of the obsidian mirror pictured here, "mirrors were also associated with Tezcatlipoca, the Aztec god of rulers, warriors and sorcerers."  Read more at their site

Duke University magazine notes: "Both reflective and translucent, the obsidian mirror was seen as a threshold between two worlds, with the obsidian conceptualized as a membrane or tissue separating this earthly world from the beyond."