General Information Zinc (Zn) is a bluish-white lustrous metal that is brittle at room temperature, but malleable when heated. It has a low melting point (419.5oC) and a moderately high specific gravity (7.13). Lead (Pb) is a soft, ductile, malleable, bluish-white metal with a low melting point (327.4oC) and a high specific gravity (11.3). Zinc and lead minerals often occur together because, as elements, they have similar chemical behavior and combine with sulfur as primary minerals. People have used zinc-bearing mineral compounds for more than 2,500 years. Only iron, aluminum, and copper are more used today. The main uses for metallic zinc are for galvanizing steel and iron, in making brass and other metal alloys, battery electrodes, sheet zinc, and as sacrificial metal to retard corrosion of ship hulls, pipelines, and other submerged or buried steelworks. Zinc compounds are ingredients in paints, rubber, chemical catalysts, fungus retardants, pharmaceuticals, electronic devices, and is the core of the U. S. penny. Lead is easily recovered from its ore minerals. The mainl use of lead is in batteries. Lead oxides are added to glass, paint, ceramics, and other chemicals to impart special properties. Lead is alloyed with antimony, copper, and bismuth to make type metal. Compounds of lead, such as carbonate and acetate, are used in drugs. Mineralogy The zinc minerals of commercial importance in Arkansas are sphalerite ((Zn,Fe)S) and smithsonite (ZnCO3). Sphalerite, contains 67.1 percent zinc, whereas smithsonite contains only 48 percent zinc. Sphalerite may contain small percentages of iron, manganese, or cadmium. Sphalerite is usually a shade of amber, has a resinous luster, and is transparent to translucent. Smithsonite is harder than sphalerite, has a glossy to pearly luster, usually is white to light brown, and is normally translucent. Some smithsonite with a striking yellow color and botryoidal habit is called "turkey fat" ore. Minor amounts of hemimorphite (Zn4Si2O7 (OH)2.H2O), were also mined in the north Arkansas zinc districts. Galena (PbS) is the only lead mineral of commercial importance in Arkansas. Galena contains about 86 percent lead, is very heavy (density of 7.4-7.6), gray in color with a metallic luster, and is easily cleaved. Silver may be an impurity, and if appreciable, it can be a by-product. Galena frequently forms with sphalerite. Arkansas Deposits Zinc and lead ores are present in the north Arkansas district, which includes Boone, Marion, Newton, Searcy, and parts of Baxter, Stone, Independence, Sharp, and Lawrence Counties, and the mineral belt of west-central Arkansas extending through and including all or parts of Pulaski, Saline, Garland, Hot Spring, Montgomery, Polk, Howard, Pike, and Sevier Counties. The north Arkansas district has been the most important commercially with more than 350 mines and prospects. The zinc and lead minerals in north Arkansas are present in irregular bodies in limestone, dolostone, and/or chert beds of Paleozoic age, often associated with local structural incongruities. Deposits have been mined from the Cotter, Powell, and Everton Formations (Ordovician), and the Boone and Batesville Sandstone Formations (Mississippian). They were mined mostly by under-ground methods, although some high-grade pockets of carbonate ore were open-pit mined. In west-central Arkansas, the zinc and lead minerals are associated with quartz veins in folded Paleozoic sandstones, shales, and novaculite. The Stanley Shale, Jackfork Sandstone, and Arkansas Novaculite host lead- and zinc-bearing quartz veins. Essentially all lead and zinc mining in the Ouachita region was by underground methods.