Calomel is a mercury chloride mineral with formula Hg2Cl2 (see mercury(I) chloride). The name derives from Greek kalos (beautiful) and melas (black) because it turns black on reaction with ammonia. This was known to alchemists. Calomel occurs as a secondary mineral which forms as an alteration product in mercury deposits. It occurs with native mercury, amalgam, cinnabar, mercurian tetrahedrite, eglestonite, terlinguaite, montroydite, kleinite, moschelite, kadyrelite, kuzminite, chursinite, kelyanite, calcite, limonite and various clay minerals. The type locality is Moschellandsburg, Alsenz-Obermoschel, Rhineland-Palatinate, Germany. History The substance later known as calomel was first documented in ancient Persia by medical historian Rhazes in year 850. Only a few of the compounds he mentioned could be positively identified as calomel, as not every alchemist disclosed what compounds they used in their drugs. Calomel first entered Western medical literature in 1608, when Oswald Croll wrote about its preparation in his Tyroncium Chemicum. It was not called calomel until 1655, when the name was created by Théodore de Mayerne, who had published its preparation and formula in “Pharmacopoeia Londinensis" in 1618. By the 19th century, calomel was viewed as a panacea, or miracle drug, and was used against almost every disease, including syphilis, bronchitis, cholera, ingrown toenails, teething, gout, tuberculosis, influenza, and cancer. During the 18th and early 19th centuries pharmacists used it sparingly; but by the late 1840s, it was being prescribed in heroic doses—due in part to the research of Benjamin Rush, who coined the term "heroic dose" to mean about 20 grains taken four times daily. This stance was supported by Dr. Samuel Cartwright, who believed that large doses were “gentlest” on the body. As calomel rose in popularity, more research was done into how it worked. J. Annesley was one of the first to write about the differering effects of calomel when taken in small or large doses. Through experimentation on dogs, Annesley concluded that calomel acted more like a laxative on the whole body rather than acting specifically on the vascular system or liver as previous physicians believed. In 1853, Samuel Jackson described the harmful effects of calomel on children in his publication for Transactions of Physicians of Philadelphia. He noted that calomel had harmful effects causing gangrene on the skin, loss of teeth, and deterioration of the gums. On May 4, 1863, William A. Hammond, the United States’ Surgeon-General, stated that calomel would no longer be used in the army