The Turba Philosophorum is one of the greatest and most well regarded texts within all of alchemy. Written around 900AD, it was quickly accepted within the chemical lexicon of the age and proceeded to vastly influence most later works. It combines veiled and metaphoric dialogue with interjecting explanations thereof delivered in the form of conversation. The subject matter ranges from the meaning of alchemical terms, to the creation of Tyrian dye, to the refining of chemical compounds, to criticism of the vulgar, or, as the Turba terms it, the envious. It treats the subject of the philosophers' stone at great length.