jet, a black amber, a black gemstone (see attestations)
teotetl = jet; it is referred to as a "special tribute to god" in the English translation by Anderson and Dibble, which also states "nowhere does a stone appear as black as this..." "perfect in its blackness" (Florentine Codex, Book 11, f. 209r-v). It is worth noting that, in the twenty-first century, there has been a move away from translating teotl as "god," in favor of divine or sacred force. But the "teotl" part in the visual representation of the teotetl in the Florentine Codex shows a horned tlacatecolotl (human-owl), suggesting that the clergy had wrought a transformation of teotl from something divine to something demonic among the students in Tenochtitlan. (summary and comment by SW)