Mystic is a city in Appanoose County, Iowa, United States. The population was 588 at the 2000 census.
At the end of the 19th century, "the valley of Walnut Creek was one continuous mining camp, known under different names, Jerome, Diamond, Mystic, Clarksdale, Rathbun and Darby" (later known as Darbyville). A. M. Elgin opened the first coal mine in the Mystic area in 1857, about 1.5 miles north of Mystic on Little Walnut Creek. The Mystic coal seam was exposed on the surface there, and drifts were opened and abandoned over the next few decades until the hills were honeycombed with mines.
In 1858, Isaac Fuller opened a large mine in Mystic, shipping coal for domestic use in nearby Centerville. In 1887, the Chicago, Milwaukee and St. Paul Railway built a line through Mystic, leading to an explosive growth in mining. By 1893, there were 14 mines in Mystic and 2 in Brazil, just to the south. It is noteworthy that the terms brass, brazzle and brazil are English dialect terms for pyrite or to coal seams with significant pyrite content and that a shale layer not far above the Mystic coal seam in Mystic and Brazil contains significant pyrite.