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Petroleum Geochemical Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
An oxide mineral consists of a closely packed structure of oxygen atoms in which positively charged cations are located in the interstices (narrow space). Silicon dioxide (SiO2) is the most important and abundant oxide existing in nature. The purest form of silicon dioxide is quartz. The next most important oxide is aluminum oxide (Al2O3), known as alumina. Both silicon and aluminum oxides are found in earth in different polymorphic forms. Sand is the crushed form of quartz. Sandstone consists of sand particles bonded together. Kieselguhr rock is made of silicon dioxide which is the remains of siliceous marine organisms. The bond between silicon and oxygen is covalent. Silicon atoms are bonded tetrahedrally to four oxygen atoms. Silicon dioxide is very hard, having a high melting point. It is the hardest substance having a crystalline structure used as a semiconductor. Aluminum oxides occur naturally in several crystalline polymorphic forms. The precious gemstones ruby and sapphire are polymorphic forms of alumina. Hematite and magnetite are well-known iron oxide minerals. Magnesium oxide (magnesia) is a white hygroscopic mineral. Pyrolusite` and ramsdellite are polymorphic minerals of manganese dioxide. In addition to these, several hundred natural oxides of various types are known. Oxides are formed either by covalent linkage or by ionic bond between oxygen free radicals (O)–2 and one or more metallic free radicals (cations). The carborundum mineral is silicon carbide (SiC) and occurs in nature as traces.
Heavy Metals
Published in Abhik Gupta, Heavy Metal and Metalloid Contamination of Surface and Underground Water, 2020
Manganese (Mn), the second most abundant heavy metal and the fourth most abundant metal after aluminum, iron, and calcium, has an atomic number of 25, an atomic weight of 54.938, and a density of 7.43 g cm–3. The oxides, carbonates, and silicates of manganese are the most common mineral sources of this metal. It can exist in eight oxidation states, the most important being +2, +3, and +7. Pyrolusite, which is manganese dioxide (MnO2), is the most important commercial source of manganese. This mineral is found in sedimentary deposits. The other, less important, sources include carbonate accumulations of rhodocrosite (MnCO3) and stratiform deposits. However, pyrolusite is mostly mined in opencast mines for extracting manganese. Manganese is used in the production of steel, especially for the production of ferromanganese alloy steels. It is used as an oxidizing agent, in dry cell batteries, in pigments, to decolorize glass and making colored glass, as a catalyst, and in fertilizers and fungicides (Encyclopaedia of Occupational Health and Safety 2012).
Was the Environmental Assessment Adequate?
Published in Karlheinz Spitz, John Trudinger, Mining and the Environment, 2019
Karlheinz Spitz, John Trudinger
Manganese is a hard gray white, brittle metal. It is an essential element for all living organisms. Some of its compounds have strong oxidizing properties. Few are toxic. Manganese is essential for the manufacture of iron and steel, and is an important characteristic of many alloys where its main contribution is to increase hardness. The oxide is used as cathode in batteries and as a pigment. Pyrolusite, an oxide of manganese, is also the main ore, from which manganese can be extracted, using acid digestion followed by electrolytic recovery.
A Review of Low Grade Manganese Ore Upgradation Processes
Published in Mineral Processing and Extractive Metallurgy Review, 2020
Veerendra Singh, Tarun Chakraborty, Sunil K Tripathy
The major manganese minerals along with their oxidation states which play a vital role during physicochemical and pyrometallurgical processing are given in Table 2. The major gangue minerals found in these ore are hematite, goethite, limonite, kaolinite, quartz, garnet, apatite, and pyrite. Properties of manganese minerals and the associated gangue minerals impact the beneficiation of low-grade manganese ores. For example, pyrolusite can be easily separated from lower density quartz by gravity methods, nevertheless it needs pyro-metallurgical processing to separate it from similar density iron minerals. The oxidation states of Mn impact the suitability of the ores for smelting reduction during the alloy production process.