M Madison County 39, 45, 58 Magnesium carbonate 12 Manganese ore 58 Marble 15, 55, 73 Marcasite 49, 51, 53, 57, 74 Maries County 27 Mark of mineral 6, 56 Metamorphic rock 15, 21, 55, 73 Metatorbernite 65 Meteorites 64 Mica 38, 39, 44, 53, 74 Microcline feldspar 44, 74 Miller County 62 Millerite 68 Mineral, definition 5, 74 Missouri Geological Survey 6, 59 Missouri School of Mines and Metallurgy 6 Moberly 33 Moniteau County 62 Morgan County 62 Muriatic acid 10 Muscovite mica 44 N Nickel 64 “Niggerheads” 32, 48 O Ochre 58 Olivine 65 Onyx 16, 42 Oolites 27, 29, 66 Orthoclase feldspar 44, 74 Osage County 26, 27 Ozora marble 15