Lead ore has a rather complex structure. It is subjected to processing for a long time and after melting polymetallic ores, lead is obtained. Judging by archaeological research, methods for extracting lead ore and the metal itself have been known since ancient times. The oldest find was found in a 6,000-year-old burial. The shape of the artifact is a rod, its handle was wooden, but had a lead tip.
Properties of lead
Pure lead is known, but extremely rare. A bluish-gray metal that has a bright metallic luster when freshly cut and oxidizes rapidly when exposed to air. It is number 82 on the chemical table. Soft, can be scratched with a nail and leaves a black streak on paper. The specific gravity of the metal is 11.40. It melts at 325°C and crystallizes upon slow cooling. It has little strength and cannot be drawn into a wire, but nevertheless it is easyrolled or pressed into thin sheets.
Its properties are significantly affected by the presence of small amounts of impurities. Lead is very easily extracted from compounds and is soluble in dilute nitric acid. It forms several compounds of commercial importance. For example, lead litharge and red lead are oxides, white lead is a basic carbonate.
Types of lead ore
Most commonly associated with zinc or silver ores is galena. Lead obtained from the latter is called "hard", and from silver-free ores - "soft". In the upper parts of the galena deposits are oxidized to numerous oxys alts. Thus, the main lead minerals are: cerussite, anglesite, pyromorphite, mimetite, vanadinite, crocoite and wulfenite.
As a rule, galena lies in deep-seated veins that have not been oxidized. When the veins are oxidized and weathered, anglesites appear as alteration products. This mineral is unstable compared to cerussite and turns into the latter when exposed to carbonized waters. Where solutions in the oxidation zone cross phosphate rocks, pyromorphite develops. Where galena contains silver, silver minerals are formed as a result of oxidation.
Some of the most important silver ores in the world are formed in this way. Numerous minerals occur together with galena in lead ore veins, one of the most commonone of them is sphalerite. The most important of the other associated minerals are calcite, dolomite, siderite, pyrite, chalcopyrite, barite and fluorite.
Mining and production technology
There are 3 main processes in lead-zinc processing: crushing, grinding and beneficiation. To produce lead, for example from galena or cerussite, the ore is first partially roasted or calcined and then smelted in reverberation or blast furnaces. Most lead ores contain silver. This metal is obtained by cupping or other methods. Sphalerite is often associated with galena, but smelters rarely take lead ores containing more than 10 percent zinc, as its presence causes difficulty in smelting. In such cases, resort to the mechanical separation of the two minerals (enrichment). Sometimes significant losses of both lead and zinc occur during this process.
When lead minerals are heated on charcoal alone, they develop a sulfur yellow crust. When heated with potassium iodide and sulfur, they create a brilliant yellow coating. Roasting with sodium carbonate and charcoal creates metallic lead, which appears as a lead gray ball that is bright when hot but dull when cold. If antimony is associated with galena, the ore is often smelted without treatment, directly to produce antimonial lead.
Applications
Metallic lead is used in the form of sheets, pipes, etc. It is used formanufacturing scales, bullets and shots. It is also a component of various alloys such as solder (lead and tin), hard metal (lead and antimony) and low-melting alloys (lead, bismuth and tin). A small amount of lead is used in the form of a basic carbonate, which is known as white lead and is very valuable as a coloring pigment. Oxides of lead, litharge and red lead are used in the manufacture of glass of excellent quality, in glazes for clay products and in the form of coloring pigments. Lead chromates are used as yellow and red paints. Lead acetate, known as lead sugar, is important in various industries.
Because of the rich lead and zinc element, lead zinc ore has excellent mining ability. It is widely used in electrical engineering, mechanical engineering, military industry, metallurgy, light industry, pharmaceutical and chemical industries. In addition, zinc metal has a wide range of applications in the nuclear and oil industries.
Ore deposits
Lead deposits are processed in three different classes, according to what they are mined: lead only, lead and zinc, lead and silver. In recent years, lead silver ores have been the largest source of the metal. Of great importance among others is the southeastern region of Missouri.
Galena is found both in layers and in veins. Metasomatic lead and zinc veins occur in contact metamorphic deposits in limestone. These are Derbyshire, Flintshire, Cumberland in England; Sale inSweden; Reibl and Blayberg (Carinthia), Leadville (Colorado), Utah, Wisconsin, etc.
Hydrothermal primordial veins are another important way galena occurs. This applies to sphalerite, pyrite, quartz and barite: deposits of Cardigan, Miner, Isle of Man, Cornwall, Derbyshire, Aspen and Rico (Colorado), Broken Hill (New South Wales) and Freiberg (Saxony). The United States of America once provided about 90% of the world's lead ore. Much less has been released recently. The countries of Spain, Australia, Germany, Poland and Mexico also produced significant amounts of lead. Followed by the UK, Russia, France, Canada, Greece and Italy.
Estimates of potential lead reserves in Russia put it in second place in the world, but in terms of production, the country ranks only seventh. The largest deposits of lead ores are located on the territory of Eastern Siberia, there are 68 of them in total.
