The East Tennessee zinc district is situated in the valley regions of the Appalachians. The outstanding structural features of the valley are folds and overthrust faults which have distributed the formations into a series of belts parallel with the long axis of the valley. The same formations, duplicated by thrust faulting, outcrop in each belt. All exposed formations are sedimentary, and most of the zinc occurrences are in the Knox dolomite or the Maynardville limestone. The ore mineral is sphalerite---lead free, and no other sulphides except minor amounts of pyrite. At present, all producing mines are in the upper 800 to 1,100 feet of the Knox dolomite, and are situated in Knox and Jefferson Counties. Five mines and two mills are in operation. The 4,000-ton Mascot mill of the American Zinc Company is supplied by ore from the Mascot, Grasselli, Athletic and Jarnigan mines. The 900-ton mill of the Universal Exploration Company is supplied by ore from its Davis mine near Jefferson City. Sphalerite is the sole primary ore mineral, and average tenors of crude ore vary from 2.5 per cent Zn to more than 5.00 per cent Zn.The orebodies are of the replacement and breccia filling type and occur in disturbed breccia zones, which are approximately parallel to the bedding. In detail, however, this long axis may be inclined to the bedding strike. The principal structural features of the ore deposits are jointing, tear faulting, low angle thrust faulting, and bedding plane movement. Associated dolomitization is conspicuous. A major overthrust fault bounds the area in semi-circle. Within this compressive area tear fault zones are the vital structural features controlling the ore.