Locations, Mining, and Formation of Sphalerite - Essay Example

Sphalerite Introduction Sphalerite is an ore of zinc, it is a mineral which consist of zinc sulfide in crystalline form along with iron. Its chemicalcomposition comprises of; Zinc 64.06% Iron 2.88% Sulfur 33.06% Making the chemical formula (Zn,Fe)S with the molecular weight of 96.98 gm. It is available in brown, yellow, red, green and black colors. It may be shiny or dull. Its luster is resinous/ greasy and has a brownish white streak. When iron content is high in sphalerite it is opaque black. Miners at times refer it as; Black jack False Galena ICSD 60378 Mock Lead Ore Matraite- densely twinned PDF 5-566 Zinc Blende Some of its specimens are fluorescent in ultraviolet light. Sphalerite's refractive index is 2.37; its crystals are in isometric crystal system and possess perfect dodecahedral cleavage. Its structure is as follows; (http://www.everyscience.com/Chemistry/Inorganic/Ionic_Solids/b.1297.php) The zinc cations (green) occupy half of the tetrahedral holes in the fcc lattice of sulphide anions (red). The crystals that are of suitable size and transparency are converted to gemstone which feature brilliant cuts to best display sphalerite's high dispersion, which is three times with that of diamond. As sphalerite is soft and fragile it is mostly best left unset as collectors or museum pieces. Gem-quality material is usually a yellowish to honey brown, red to orange, or green Formation There are a number of ways sphalerite is formed; bacteria also play a role in its formation. In the regions where there is low oxygen solution such as flooded tunnels the bacteria's take in zinc and sulfur from the water and combine them to create a byproduct of sphalerite known as sulfide, which reacts with the metals including zinc creating insoluble products. This build up of microbial precipitation by the bacteria have led to the discovery of large zinc sulfide deposits by the miners. The biofilm formed is grey in color and is further developed naturally to form sphalerite. Sphalerite is a cubic crystal with zinc and sulfur atoms tetrahedrally coordinated. This structure is similar to that of diamond. The hexagonal analogue is known as wurtzite structure. The lattice constant for zinc sulfide in the zincblende crystal structure is 0.596 nm, calculated from geometry and ionic radii of 0.074nm (zinc) and 0.184nm (sulfide). It forms ABCABC layers. Mining Sphalerite is obtained from underground mining. It is the ore of zinc that is formed in veins which are layers of rocks and minerals formed underground. It is found in sedimentary, igneous and metamorphic rocks. Sphalarite accumulates in deposits which can extend far underground. Thus underground mining is most suitable; other methods would be too expensive and difficult. The underground excavation is determined by strip ratio method which is the total amount of waste materials that need to be removed in proportion the amount of ore. Thus minimum possible waste is extracted. The underground mine of sphalerite consist of sophisticated network of tunnels, shafts and equipments. It is entered through a shaft, a horizontal tunnel or an adit which is a horizontal entry way. There are several levels in the underground mine and sphalerite in mined in rooms called stopes. It is drilled and blasted out taking care of the ceiling so that the mine does not collapse. Sphalarite mining process involves a number of equipments. Continuous mining machines are used which cut through rocks and pull them up, even separating the unusable ore from waste rock all in one system. Dump trucks are used in the mine to carry material to appropriate locations to different parts of the mine. At times shuttle cars are also used. Today in the modern era mining is a highly technological and mechanized process. Sophisticated vehicles, rail systems and state-of-the-art drilling systems are bought from manufacturers and suppliers. Ventilation systems pump in fresh air while removing poisonous gases and dust. Also, the roof is supported by timber, concrete or even steel supports. Steel rods are often used to hold the roof to the interior rocks. The current methods of underground mining make sphalarite mining relatively safe. It is a productive process and it needs to be, since the ore is so commonly used to make many products that industry and consumers depend on. Locations The places where sphalerite is found are; Trepca, former Yugoslavia; Alston Moor, England; Binnental, Wallis, Switzerland; and Broken Hill, New South Wales, Australia. Spectacular transparent yellow, orange, and red crystals come from Santander, Spain. In Mexico, large iron-rich, metallic lustered crystals associated with Galena were found in Mazapil, Zacatecas, and green crystals, often twinned, in Cananea, Sonora. In the U.S., some of the finest specimens come from the tri-state mining district of Missouri, Kansas, and Oklahoma. These areas include the Joplin area, Jasper Co., Missouri; Treece, Galena, and Baxter Springs, Cherokee Co., Kansas; and Picher, Ottawa Co., Oklahoma. Much Sphalerite has come from the Balmat area, St. Lawrence Co., New York; and dark green crystals from the Iron Cap Mine in Graham Co., Arizona. Many specimens are from Franklin and Ogdensburg, Sussex Co., New Jersey, including pale green Cleiophane crystals. Superb examples of this mineral were found in the Elmwood Mine, Carthage, Smith Co., Tennessee. The Fluorite mines of Hardin Co., Illinois, have also produced quality Sphalerite. Lustrous brownish crystals are also found in the Redland Quarry, Niagara Falls, New York. In Canada, good examples of this mineral come from Mont Saint Hilaire, Quebec. The transparent varieties are available only in Mexico and Spain Uses Sphalerite is a zinc iron sulfide (ZnS) crystal found in a variety of colors including black, brown, red, orange, yellow, green and gray. It can also be colorless, but that is a rare occurrence. It is the main ore of zinc, which lends it to uses in metallurgy. In industries it is a chief source of zinc; it is used mainly for metallurgy. The zinc present is used to coat metals to resist corrosion and can also be used to make metal blends. Further ahead zinc extracted from sphalerite is used in dietary supplement and rust proofing material. Usually it is used to make copper, silver and lead. Sphalerite is also used to make batteries, brass, pigments and medicine. Sphalerite's commercial use is that it has a high refractive index of 2.37 to 2.42 which makes it a very sparkling crystal. Thus gemologists add sphalerite to their collections as it can be polished to give beautiful and sparkling appearance. Sphalerite is also cut and used in jewellery. Sphalerite becomes a major ore of those metals which are present as impurities in it. Work cited 1. Dana's Manual of Mineralogy ISBN 0-471-03288-3 2. The handbook of mineralogy, sphalerite, mineral data publishing, version 1, 2001-2005. 3. Webster, R., Read, P. G. Ed, Gems: Their sources, descriptions and identification (5th ed.), p. 386. Butterworth-Heinemann, Great Britain. ISBN 0-7506-1674-1,2000 4. Sphalerite, the mineral and gemstone kingdom, http://www.minerals.net/mineral/sulfides/sphaleri/sphaleri.htm Read More