Lead. Galena PbS 86.6 p.c. Cerussite PbCO{3} 77.5 p.c. Anglesite PbSO{4} 67.7 p.c. Pyromorphite Pb{3}P{2}O{8} plus 1/3 PbCl{2} 75.36 p.c. Lead ores are frequently rich in silver. They occur in limestone, sandstone, granite and clay. The commercial ores are galena, which is easily recognized by its steel-like cubes, and the carbonates. These latter are like lightly colored clays when in powder and are very apt to be overlooked. Fluor spar is as favorable a gangue for lead as quartz is for gold. The Rocky Mountains are the principal American sources of this metal, but a very large amount comes from the Mississippi valley. In the mountains the ore is a by-product, in silver smelting, being obtained from argentiferous galena, while in Missouri, Kansas, Wisconsin and Illinois lead and zinc are found free from any mixture with the precious metal. The age of these deposits varies from lower silurian or cambrian to the carboniferous. The ore is found in limestone rocks,--sometimes in flat openings parallel to the almost horizontal beds, or else in gash veins almost at right angles to these. As lead is often found in dolomite limestone, that is, limestone carrying almost as much magnesia as lime, and this rock was undoubtedly deposited in a shallow sea, geologists incline to the belief that therefore the lead is due to a growth of seaweeds in whose ash this metal and zinc are known to occur. At any rate, these deposits now have great economic value, and the lead and zinc ore is easily got at. Galena and zinc blende frequently resemble one another, but they may be distinguished by this infallible sign: the powder of galena is black, and that of blende brown, or yellow. Lithographic Stone. This is a very fine grained compact limestone from Bavaria. So far nothing equal to the imported stone has been found in America. The distinguishing qualities are: Gray, drab or yellow; porous, yet not too soft; of fine texture, and free from veins and inequalities. Manganese. Manganese ores in 1899 amounted in the United States to 143,256 tons, value $306,476. This mineral is used for bleaching and making oxygen, and in steel manufacture. Pyrolusite contains 63 per cent. manganese. Hardness, 2.3. Specific gravity, 4.8. Luster, metallic. Opaque. Gray to bluish black. Harsh. Brittle. Cleavage, imperfect. Fracture, uneven. Granular, massive. Manganite is harder, 4.0; its specific gravity is 4.3. Luster, sub-metallic. Cleavage, perfect. Texture, fibrous. Wad is an impure ore of manganese found in bogs, of little or no value. Pyrolusite MnO{2} 63.2 Braunite Mn{2}O{3} 69.68 Psilomelane (Variable) ?