The Bureau of Mines investigated the mineralogy, tonnage, and beneficiating characteristics of oxidized (nonmagnetic) taconite iron resources of the Western Mesabi Range. Magnetic taconite currently provides about 95 pct of Mesabi production, but the large tonnages of oxidized taconite between the magnetic deposits will be needed to help meet future domestic demand for iron ore. Three bulk samples that represent large tonnages from the Western Mesabi Range were selected to determine their mineral composition and liberation by light optical microscopy and to test their beneficiating response. This report describes the mineralogy and liberation characteristics of the three samples of the Biwabik Iron Formation for 26.5 Mi (42.7 Km) from Keewatin to Grand Rapids, Minnesota. (Details of response to beneficiation were reported previously.) The samples represent mostly material from the lower cherty member of the Biwabik Iron Formation, although one sample included some upper cherty member. Minerals of all three samples were quartz (chert), hematite, geothite, and minor to trace amounts of magnetite, iron carbonate, and iron silicates. The oxidized taconites of the Western Mesabi Range represent a subeconomic indicated resource that can be selectively mined and beneficiated as a future large source of iron feed for steelmaking.