At least 11 artificial sulfosalts have been prepared by heating various mixtures of galena, stibnite, and orpiment in closed tubes. Among these are the new Madoc sulfosalts playfairite, madocite, guettardite, and two lead sulfantimonides which have no mineral counterparts. From oldest to youngest, the depositional sequence at Madoc is sulfides, arsenic-rich sulfosalts, and antimony-rich and copper-bearing sulfosalts. Precipitation of the Pb-Sb-As sulfosalts initially followed a trend of decreasing activity of As 2 S 3 and probably terminated with increasing activity of Sb 2 S 3 in the system. The observed paragenesis is believed to have resulted principally from the greater solubility of arsenic as compared to antimony, with temperature effects becoming a more important control toward the terminal stages of deposition.