Mesabi (məsäbˈē) [key], range of low hills, NE Minn., once famous for its extensive iron ore deposits. The ores were found in a belt c.110 mi (180 km) long and from 1 to 3 mi (1.6–4.8 km) wide between Babbitt and Grand Rapids, occurring in horizontal layers (up to 500 ft/152 m thick) near the surface and mined by the open pit method. Reserves of high-grade hematite iron are now exhausted, and lower-grade taconite deposits are being worked. The taconite contains mostly chert and magnetite (an iron-bearing mineral) and must undergo a costly and complex beneficiation process before being shipped in the form of pellets containing c.60% iron. Most of the ore found is shipped by rail to Duluth, Minn., and other ports on Lake Superior. The Mesabi iron ore deposits were first discovered in 1887 by Leonidas Merritt and his brothers, who organized the Mountain Iron Company in 1890 to mine the ore; John D. Rockefeller gained control of the company in the Panic of 1893.