Sphalerite | |
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General | |
Category | Sulfide mineral |
Formula (repeating unit) | (Zn,Fe)S |
IMA symbol | Sp [1] |
Strunz classification | 2.CB.05a |
Dana classification | 02.08.02.01 |
Crystal system | Cubic |
Crystal class | Hextetrahedral (43m) H-M symbol: (4 3m) |
Space group | F43m (No. 216) |
Unit cell | a = 5.406 Å; Z = 4 |
Structure | |
Jmol (3D) | Interactive image |
Identification | |
Color | Light to dark brown, red-brown, yellow, red, green, light blue, black and colourless. |
Crystal habit | Euhedral crystals – occurs as well-formed crystals showing good external form. Granular – generally occurs as anhedral to subhedral crystals in matrix. |
Twinning | Simple contact twins or complex lamellar forms, twin axis [111] |
Cleavage | perfect dodecahedral on [011] |
Fracture | Uneven to conchoidal |
Mohs scale hardness | 3.5–4 |
Luster | Adamantine, resinous, greasy |
Streak | brownish white, pale yellow |
Diaphaneity | Transparent to translucent, opaque when iron-rich |
Specific gravity | 3.9–4.2 |
Optical properties | Isotropic |
Refractive index | nα = 2.369 |
Other characteristics | non-radioactive, non-magnetic, fluorescent and triboluminescent. |
References | [2] [3] [4] |
Sphalerite is a sulfide mineral with the chemical formula (Zn, Fe)S . [5] It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Valley type, and volcanogenic massive sulfide deposits. It is found in association with galena, chalcopyrite, pyrite (and other sulfides), calcite, dolomite, quartz, rhodochrosite, and fluorite. [6]
German geologist Ernst Friedrich Glocker discovered sphalerite in 1847, naming it based on the Greek word sphaleros, meaning "deceiving", due to the difficulty of identifying the mineral. [7]
In addition to zinc, sphalerite is an ore of cadmium, gallium, germanium, and indium. Miners have been known to refer to sphalerite as zinc blende, black-jack, and ruby blende . [8] Marmatite is an opaque black variety with a high iron content. [9]
Sphalerite crystallizes in the face-centered cubic zincblende crystal structure, [10] which named after the mineral. This structure is a member of the hextetrahedral crystal class (space group F43m). In the crystal structure, both the sulfur and the zinc or iron ions occupy the points of a face-centered cubic lattice, with the two lattices displaced from each other such that the zinc and iron are tetrahedrally coordinated to the sulfur ions, and vice versa. [11] Minerals similar to sphalerite include those in the sphalerite group, consisting of sphalerite, colaradoite, hawleyite, metacinnabar, stilleite and tiemannite. [12] The structure is closely related to the structure of diamond. [10] The hexagonal polymorph of sphalerite is wurtzite, and the trigonal polymorph is matraite. [12] Wurtzite is the higher temperature polymorph, stable at temperatures above 1,020 °C (1,870 °F). [13] The lattice constant for zinc sulfide in the zinc blende crystal structure is 0.541 nm. [14] Sphalerite has been found as a pseudomorph, taking the crystal structure of galena, tetrahedrite, barite and calcite. [13] [15] Sphalerite can have Spinel Law twins, where the twin axis is [111].
The chemical formula of sphalerite is (Zn,Fe)S; the iron content generally increases with increasing formation temperature and can reach up to 40%. [6] The material can be considered a ternary compound between the binary endpoints ZnS and FeS with composition ZnxFe(x-1)S, where x can range from 1 (pure ZnS) to 0.6.[ citation needed ]
All natural sphalerite contains concentrations of various impurities, which generally substitute for zinc in the cation position in the lattice; the most common cation impurities are cadmium, mercury and manganese, but gallium, germanium and indium may also be present in relatively high concentrations (hundreds to thousands of ppm). [16] [17] Cadmium can replace up to 1% of zinc and manganese is generally found in sphalerite with high iron abundances. [12] Sulfur in the anion position can be substituted for by selenium and tellurium. [12] The abundances of these impurities are controlled by the conditions under which the sphalerite formed; formation temperature, pressure, element availability and fluid composition are important controls. [17]
Sphalerite possesses perfect dodecahedral cleavage, having six cleavage planes. [10] [18] In pure form, it is a semiconductor, but transitions to a conductor as the iron content increases. [19] It has a hardness of 3.5 to 4 on the Mohs scale of mineral hardness. [20]
It can be distinguished from similar minerals by its perfect cleavage, its distinctive resinous luster, and the reddish-brown streak of the darker varieties. [21]
Pure zinc sulfide is a wide-bandgap semiconductor, with bandgap of about 3.54 electron volts, which makes the pure material transparent in the visible spectrum. Increasing iron content will make the material opaque, while various impurities can give the crystal a variety of colors. [20] In thin section, sphalerite exhibits very high positive relief and appears colorless to pale yellow or brown, with no pleochroism. [6]
The refractive index of sphalerite (as measured via sodium light, average wavelength 589.3 nm) ranges from 2.37 when it is pure ZnS to 2.50 when there is 40% iron content. [6] Sphalerite is isotropic under cross-polarized light, however sphalerite can experience birefringence if intergrown with its polymorph wurtzite; the birefringence can increase from 0 (0% wurtzite) up to 0.022 (100% wurtzite). [6] [13]
Depending on the impurities, sphalerite will fluoresce under ultraviolet light. Sphalerite can be triboluminescent. [22] Sphalerite has a characteristic triboluminescence of yellow-orange. Typically, specimens cut into end-slabs are ideal for displaying this property.[ citation needed ]
Gemmy, colorless to pale green sphalerite from Franklin, New Jersey (see Franklin Furnace), are highly fluorescent orange and/or blue under longwave ultraviolet light and are known as cleiophane, an almost pure ZnS variety. [23] Cleiophane contains less than 0.1% of iron in the sphalerite crystal structure. [12] Marmatite or christophite is an opaque black variety of sphalerite and its coloring is due to high quantities of iron, which can reach up to 25%; marmatite is named after Marmato mining district in Colombia and christophite is named for the St. Christoph mine in Breitenbrunn, Saxony. [23] Both marmatite and cleiophane are not recognized by the International Mineralogical Association (IMA). [24] Red, orange or brownish-red sphalerite is termed ruby blende or ruby zinc, whereas dark colored sphalerite is termed black-jack. [23]
Sphalerite is amongst the most common sulfide minerals, and it is found worldwide and in a variety of deposit types. [8] The reason for the wide distribution of sphalerite is that it appears in many types of deposits; it is found in skarns, [25] hydrothermal deposits, [26] sedimentary beds, [27] volcanogenic massive sulfide deposits (VMS), [28] Mississippi-valley type deposits (MVT), [29] [30] granite [12] and coal. [31]
Approximately 50% of zinc (from sphalerite) and lead comes from Sedimentary exhalative (SEDEX) deposits, which are stratiform Pb-Zn sulfides that form at seafloor vents. [32] The metals precipitate from hydrothermal fluids and are hosted by shales, carbonates and organic-rich siltstones in back-arc basins and failed continental rifts. [33] The main ore minerals in SEDEX deposits are sphalerite, galena, pyrite, pyrrhotite and marcasite, with minor sulfosalts such as tetrahedrite-freibergite and boulangerite; the zinc + lead grade typically ranges between 10 and 20%. [33] Important SEDEX mines are Red Dog in Alaska, Sullivan Mine in British Columbia, Mount Isa and Broken Hill in Australia and Mehdiabad in Iran. [34]
Similar to SEDEX, Mississippi-Valley type (MVT) deposits are also a Pb-Zn deposit which contains sphalerite. [35] However, they only account for 15–20% of zinc and lead, are 25% smaller in tonnage than SEDEX deposits and have lower grades of 5–10% Pb + Zn. [33] MVT deposits form from the replacement of carbonate host rocks such as dolostone and limestone by ore minerals; they are located in platforms and foreland thrust belts. [33] Furthermore, they are stratabound, typically Phanerozoic in age and epigenetic (form after the lithification of the carbonate host rocks). [36] The ore minerals are the same as SEDEX deposits: sphalerite, galena, pyrite, pyrrhotite and marcasite, with minor sulfosalts. [36] Mines that contain MVT deposits include Polaris in the Canadian arctic, Mississippi River in the United States, Pine Point in Northwest Territories, and Admiral Bay in Australia. [37]
Volcanogenic massive sulfide (VMS) deposits can be Cu-Zn- or Zn-Pb-Cu-rich, and accounts for 25% of Zn in reserves. [33] There are various types of VMS deposits with a range of regional contexts and host rock compositions; a common characteristic is that they are all hosted by submarine volcanic rocks. [32] They form from metals such as copper and zinc being transferred by hydrothermal fluids (modified seawater) which leach them from volcanic rocks in the oceanic crust; the metal-saturated fluid rises through fractures and faults to the surface, where it cools and deposits the metals as a VMS deposit. [38] The most abundant ore minerals are pyrite, chalcopyrite, sphalerite and pyrrhotite. [33] Mines that contain VMS deposits include Kidd Creek in Ontario, Urals in Russia, Troodos in Cyprus, and Besshi in Japan. [39]
The top producers of sphalerite include the United States, Russia, Mexico, Germany, Australia, Canada, China, Ireland, Peru, Kazakhstan and England. [40] [41]
Sources of high quality crystals include:
Place | Country |
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Freiberg, Saxony, Neudorf, Harz Mountains | Germany |
Lengenbach Quarry, Binntal, Valais | Switzerland |
Horní Slavkov and Příbram | Czech Republic |
Rodna | Romania |
Madan, Smolyan Province, Rhodope Mountains | Bulgaria |
Aliva mine, Picos de Europa Mountains, Cantabria [Santander] Province | Spain |
Alston Moor, Cumbria | England |
Dalnegorsk, Primorskiy Kray | Russia |
Watson Lake, Yukon Territory | Canada |
Flin Flon, Manitoba | Canada |
Tri-State district including deposits near Baxter Springs, Cherokee County, Kansas; Joplin, Jasper County, Missouri and Picher, Ottawa County, Oklahoma | US |
Elmwood mine, near Carthage, Smith County, Tennessee | US |
Eagle mine, Gilman district, Eagle County, Colorado | US |
Santa Eulalia, Chihuahua | Mexico |
Naica, Chihuahua | Mexico |
Cananea, Sonora | Mexico |
Huaron | Peru |
Casapalca | Peru |
Huancavelica | Peru |
Zinkgruvan | Sweden |
Sphalerite is an important ore of zinc; around 95% of all primary zinc is extracted from sphalerite ore. [42] However, due to its variable trace element content, sphalerite is also an important source of several other metals such as cadmium, [43] gallium, [44] germanium, [45] and indium [46] which replace zinc. The ore was originally called blende by miners (from German blind or deceiving) because it resembles galena but yields no lead. [21]
The zinc in sphalerite is used to produce brass, an alloy of copper with 3–45% zinc. [18] Major element alloy compositions of brass objects provide evidence that sphalerite was being used to produce brass by the Islamic as far back as the medieval ages between the 7th and 16th century CE. [47] Sphalerite may have also been used during the cementation process of brass in Northern China during the 12th–13th century CE (Jin Dynasty). [48] Besides brass, the zinc in sphalerite can also be used to produce certain types of bronze; bronze is dominantly copper which is alloyed with other metals such as tin, zinc, lead, nickel, iron and arsenic. [49]
Gallium is a chemical element; it has the symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, gallium is in group 13 of the periodic table and is similar to the other metals of the group.
Germanium is a chemical element; it has symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors silicon and tin. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature.
Ore is natural rock or sediment that contains one or more valuable minerals concentrated above background levels, typically containing metals, that can be mined, treated and sold at a profit. The grade of ore refers to the concentration of the desired material it contains. The value of the metals or minerals a rock contains must be weighed against the cost of extraction to determine whether it is of sufficiently high grade to be worth mining and is therefore considered an ore. A complex ore is one containing more than one valuable mineral.
Chalcopyrite ( KAL-kə-PY-ryte, -koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green-tinged black.
Greenockite, also cadmium blende or cadmium ochre (obsolete) is a rare cadmium bearing metal sulfide mineral consisting of cadmium sulfide (CdS) in crystalline form. Greenockite crystallizes in the hexagonal system. It occurs as massive encrustations and as hemimorphic six-sided pyramidal crystals which vary in color from a honey yellow through shades of red to brown. The Mohs hardness is 3 to 3.5 and the specific gravity is 4.8 to 4.9.
Hemimorphite is the chemical compound Zn4(Si2O7)(OH)2·H2O, a component of mineral calamine. It is a silicate mineral which, together with smithsonite (ZnCO3), has been historically mined from the upper parts of zinc and lead ores. Both compounds were originally believed to be the same mineral and classified as calamine. In the second half of the 18th century, it was discovered that these two different compounds were both present in calamine. They closely resemble one another.
Germanite is a rare copper iron germanium sulfide mineral, Cu26Fe4Ge4S32. It was first discovered in 1922, and named for its germanium content. It is only a minor source of this important semiconductor element, which is mainly derived from the processing of the zinc sulfide mineral sphalerite. Germanite contains gallium, zinc, molybdenum, arsenic, and vanadium as impurities.
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver.
Zinc sulfide is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite. Although this mineral is usually black because of various impurities, the pure material is white, and it is widely used as a pigment. In its dense synthetic form, zinc sulfide can be transparent, and it is used as a window for visible optics and infrared optics.
Wurtzite is a zinc and iron sulfide mineral with the chemical formula (Zn,Fe)S, a less frequently encountered structural polymorph form of sphalerite. The iron content is variable up to eight percent. It is trimorphous with matraite and sphalerite.
Volcanogenic massive sulfide ore deposits, also known as VMS ore deposits, are a type of metal sulfide ore deposit, mainly copper-zinc which are associated with and produced by volcanic-associated hydrothermal events in submarine environments.
Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.
Sedimentary exhalative deposits are zinc-lead deposits originally interpreted to have been formed by discharge of metal-bearing basinal fluids onto the seafloor resulting in the precipitation of mainly stratiform ore, often with thin laminations of sulfide minerals. SEDEX deposits are hosted largely by clastic rocks deposited in intracontinental rifts or failed rift basins and passive continental margins. Since these ore deposits frequently form massive sulfide lenses, they are also named sediment-hosted massive sulfide (SHMS) deposits, as opposed to volcanic-hosted massive sulfide (VHMS) deposits. The sedimentary appearance of the thin laminations led to early interpretations that the deposits formed exclusively or mainly by exhalative processes onto the seafloor, hence the term SEDEX. However, recent study of numerous deposits indicates that shallow subsurface replacement is also an important process, in several deposits the predominant one, with only local if any exhalations onto the seafloor. For this reason, some authors prefer the term clastic-dominated zinc-lead deposits. As used today, therefore, the term SEDEX is not to be taken to mean that hydrothermal fluids actually vented into the overlying water column, although this may have occurred in some cases.
Seafloor massive sulfide deposits or SMS deposits, are modern equivalents of ancient volcanogenic massive sulfide ore deposits or VMS deposits. The term has been coined by mineral explorers to differentiate the modern deposit from the ancient.
Carbonate-hosted lead-zinc ore deposits are important and highly valuable concentrations of lead and zinc sulfide ores hosted within carbonate formations and which share a common genetic origin.
The Broken Hill Ore Deposit is located underneath Broken Hill in western New South Wales, Australia, and is the namesake for the town. It is arguably the world's richest and largest zinc-lead ore deposit.
Coloradoite, also known as mercury telluride (HgTe), is a rare telluride ore associated with metallic deposit. Gold usually occurs within tellurides, such as coloradoite, as a high-finess native metal.
Hydrothermal mineral deposits are accumulations of valuable minerals which formed from hot waters circulating in Earth's crust through fractures. They eventually produce metallic-rich fluids concentrated in a selected volume of rock, which become supersaturated and then precipitate ore minerals. In some occurrences, minerals can be extracted for a profit by mining. Discovery of mineral deposits consumes considerable time and resources and only about one in every one thousand prospects explored by companies are eventually developed into a mine. A mineral deposit is any geologically significant concentration of an economically useful rock or mineral present in a specified area. The presence of a known but unexploited mineral deposit implies a lack of evidence for profitable extraction.
Massive sulfide deposits are ore deposits that have significant stratiform ore bodies consisting mainly of sulfide minerals. Most massive sulfide ore deposits have other portions that are not massive, including stringer or feeder zones beneath the massive parts that mostly consist of crosscutting veins and veinlets of sulfides in a matrix of pervasively altered host rock and gangue.
Chvilevaite (Russian: чвилеваи́т, чвилёваи́т, in its own name) is a rare hydrothermal polymetallic mineral from the class of complex sulfides, forming microscopic grains in related minerals, its composition is a rare combination of alkali (combining lithophile) and chalcophile metals — sodium ferro-sulfide, zinc and copper with the calculation formula Na(Cu,Fe,Zn)2S4, originally published and confirmed as Na(Cu,Fe,Zn)2S2.
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