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Covellite
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<h2 id="composition">Composition</h2> <p>Covellite belongs to the binary copper sulfides group, which has the formula CuxSy and can have a wide-ranging copper/sulfur ratio, from 1:2 to 2:1 (Cu/S). However, this series is by no means continuous and the homogeneity range of covellite CuS is narrow. Materials rich in sulfur CuSx where x~ 1.1- 1.2 do exist, but they exhibit "<a href="/facts/Superstructure_(condensed_matter)/o2yMY7NT">superstructures</a>", a modulation of the hexagonal ground plane of the structure spanning a number of adjacent unit cells.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> This indicates that several of covellite's special properties are the result of molecular structure at this level. </p><p>As described for <a href="/facts/Copper_monosulfide/vYzbUso6">copper monosulfide</a>, the assignment of formal <a href="/facts/Oxidation_state/W53W6s6V">oxidation states</a> to the atoms that constitute covellite is deceptive.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> The formula might seem to suggest the description Cu2+, S2−. In fact the <a href="/facts/Atomic_structure/FoQ4kGN5">atomic structure</a> shows that copper and sulfur each adopt two different geometries. However <a href="/facts/Photoelectron_spectroscopy/UPvrQ8zD">photoelectron spectroscopy</a>, <a href="/facts/Magnetism/eo75vApl">magnetic</a>, and <a href="/facts/Electrical/hNC8D65W">electrical</a> properties all indicate the <i>absence</i> of Cu2+ (d9) ions.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> In contrast to the oxide CuO, the material is not a magnetic <a href="/facts/Semiconductor/zFf3mGTE">semiconductor</a> but a metallic conductor with weak <a href="/facts/Pauli_paramagnetism/vj1SMbbp">Pauli-paramagnetism</a>.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> Thus, the mineral is better described as consisting of Cu+ and S− rather than Cu2+ and S2−. Compared to pyrite with a non-closed shell of S− pairing to form S22−, there are only 2/3 of the sulfur atoms held.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> The other 1/3 remains unpaired and together with Cu atoms forms hexagonal layers reminiscent of the boron nitride (graphite structure).<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> Thus, a description Cu+3S−S22− would seem appropriate with a delocalized hole in the <a href="/facts/Valence_band/2NUALlHJ">valence band</a> leading to metallic conductivity. Subsequent band structure calculations indicate however that the hole is more localized on the sulfur pairs than on the unpaired sulfur. This means that Cu+3S2−S2− with a mixed sulfur oxidation state −2 and −1/2 is more appropriate. Despite the extended formula of Cu+3S2−S2− from researchers in 1976 and 1993, others have come up with variations, such as Cu+4Cu2+2(S2)2S2.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a><a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <h2 id="structure">Structure</h2> <p>For a copper sulfide, covellite has a complicated lamellar structure, with alternating layers of CuS and Cu2S2 with copper atoms of trigonal planar (uncommon) and tetrahedral coordination respectively.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> The layers are connected by S-S bonds (based on Van der Waals forces) known as S2 dimers.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> The Cu2S2 layers only has one l/3 bond along the c-axis (perpendicular to layers), thus only one bond in that direction to create a perfect cleavage {0001}.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> The conductivity is greater across layers due to the partially filled 3p orbitals, facilitating electron mobility.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> </p> <h2 id="formation">Formation</h2> <h3>Naturally occurring</h3> <p>Covellite is commonly found as a secondary copper mineral in deposits. Covellite is known to form in <a href="/facts/Weathering/uSYGlv0H">weathering</a> environments in surficial deposits where copper is the primary sulfide.<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> As a primary mineral, the formation of covellite is restricted to <a href="/facts/Hydrothermal/hqwwksSm">hydrothermal</a> conditions, thus rarely found as such in copper ore deposits or as a volcanic sublimate.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> </p> <h3>Synthetic</h3> <p>Covellite's unique crystal structure is related to its complex <a href="/facts/Oxidative/Pyd5RVcj">oxidative</a> formation conditions, as seen when attempting to synthesize covellite.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> Its formation also depends on the state and history of the associated sulfides it was derived from. Experimental evidence shows <a href="/facts/Ammonium_metavanadate/GrDHx3Qh">ammonium metavanadate</a> (NH4VO3) to be a potentially important <a href="/facts/Catalyst/LPBS7TQC">catalyst</a> for covellite's solid state transformation from other copper sulfides.<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> Researchers discovered that covellite can also be produced in the lab under <a href="/facts/Hypoxia_(environmental)/VSSWPNlF">anaerobic</a> conditions by sulfate reducing bacteria at a variety of temperatures.<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> However, further research remains, because although the abundance of covellite may be high, the growth of its crystal size is actually inhibited by physical constraints of the bacteria.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> It has been experimentally demonstrated that the presence of ammonium vanadates is important in the solid state transformation of other copper sulfides to covellite crystals.<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> </p> <h2 id="occurrence">Occurrence</h2> <p>Covellite's occurrence is widespread around the world, with a significant number of localities in <a href="/facts/Central_Europe/VdxzSbJz">Central Europe</a>, <a href="/facts/China/lTjIXY5p">China</a>, <a href="/facts/Australia/qLHpbppq">Australia</a>, <a href="/facts/Western_United_States/uY9UGAus">Western United States</a>, and <a href="/facts/Argentina/aFSA5bAk">Argentina</a>.<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a> Many are found close to <a href="/facts/Orogenic_belts/XrvRMpsw">orogenic belts</a>, where <a href="/facts/Orographic_precipitation/avly8ef3">orographic precipitation</a> often plays a role in weathering. An example of primary mineral formation is in hydrothermal veins at depths of 1,150 m found in Silver Bow County, Montana.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a> As a secondary mineral, covellite also forms as descending surface water in the <a href="/facts/Supergene_(geology)/Y6lpdfB3">supergene</a> enrichment zone oxidizes and redeposits covellite on <a href="/facts/Hypogene/rA6MX4Ws">hypogene</a> sulfides (pyrite and chalcopyrite) at the same locality.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> An unusual occurrence of covellite was found replacing <a href="/facts/Organic_material/t17tVCvk">organic debris</a> in the <a href="/facts/Red_bed/C1xMjRgv">red beds</a> of <a href="/facts/New_Mexico/wosJCGaW">New Mexico</a>.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> </p><p>Nicola Covelli (1790-1829), the discoverer of the mineral, was a professor of botany and chemistry though was interested in geology and volcanology, particularly Mount Vesuvius' eruptions.<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> His studies of its lava led to the discovery of several unknown minerals including covellite.<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> </p> <h2 id="applications">Applications</h2> <h3>Superconductors</h3> <p>Covellite was the first identified naturally occurring <a href="/facts/Superconductor/pqQAlSzJ">superconductor</a>.<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a> The framework of CuS3 /CuS2 allow for an electron excess that facilitate superconduction during particular states, with exceptionally low thermal loss. Material science is now aware of several of covellite's favorable properties and several researchers are intent on synthesizing covellite.<a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a><a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a> Uses of covellite CuS superconductivity research can be seen in <a href="/facts/Lithium_battery/D5yfo8XS">lithium batteries</a>’ <a href="/facts/Cathode/tqdlGayU">cathodes</a>, <a href="/facts/Ammonium/jYm8wc1n">ammonium</a> <a href="/facts/Gas_sensors/QHH5sQgp">gas sensors</a>, and <a href="/facts/Solar_electric/3L814UCC">solar electric devices</a> with metal <a href="/facts/Chalcogenide/GTXXbDoV">chalcogenide</a> thin films.<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a><a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a><a class="footnote-ref" id="fnref:36" href="#fn:36"><sup>36</sup></a> </p> <h3>Lithium ion batteries</h3> <p>Research into alternate cathode material for <a href="/facts/Lithium_batteries/D5yfo8XS">lithium batteries</a> often examines the complex variations in stoichiometry and <a href="/facts/Tetrahedron_packing/8ECo5hsN">tetrahedron</a> layered structure of copper sulfides.<a class="footnote-ref" id="fnref:37" href="#fn:37"><sup>37</sup></a> Advantages include limited toxicity and low costs.<a class="footnote-ref" id="fnref:38" href="#fn:38"><sup>38</sup></a> The high <a href="/facts/Electrical_conductivity/akyCKvMy">electrical conductivity</a> of covellite (10−3 S cm−1) and a high theoretical <a href="/facts/Capacity_factor/5DPMh92l">capacity</a> (560 mAh g−1) with flat discharge curves when cycled versus Li+/Li has been determined to play critical roles for capacity.<a class="footnote-ref" id="fnref:39" href="#fn:39"><sup>39</sup></a> The variety of methods of formations is also a factor of the low costs. However, issues with cycle stability and <a href="/facts/Chemical_kinetics/D8vyX4aE">kinetics</a> have been limiting the progress of utilizing covellite in mainstream lithium batteries until future developments in its research.<a class="footnote-ref" id="fnref:40" href="#fn:40"><sup>40</sup></a> </p> <h3>Nanostructures</h3> <p>The <a href="/facts/Electron_mobility/aN3bco00">electron mobility</a> and free hole density characteristics of covellite makes it an attractive choice for <a href="/facts/Nanostructure/rkeQGqt7">nanoplatelets</a> and nanocrystals because they provide the structures the ability to vary in size.<a class="footnote-ref" id="fnref:41" href="#fn:41"><sup>41</sup></a><a class="footnote-ref" id="fnref:42" href="#fn:42"><sup>42</sup></a> However, this ability can be limited by the plate-like structure all copper sulfides possess.<a class="footnote-ref" id="fnref:43" href="#fn:43"><sup>43</sup></a> Its <a href="/facts/Anisotropy/YMqTQWVB">anisotropic</a> electrical conductivity has been experimentally proven to be greater within layers (i.e. perpendicular to c-axis).<a class="footnote-ref" id="fnref:44" href="#fn:44"><sup>44</sup></a> Researchers have shown that covellite nanoplatelets of approx. two nm thick, with one unit cell and two copper atoms layers, and diameters around 100 nm are ideal dimensions for <a href="/facts/Electrocatalyst/UXwuCNNg">electrocatalysts</a> in <a href="/facts/Oxygen_reduction_reaction/9uv5EMho">oxygen reduction reactions</a> (ORR).<a class="footnote-ref" id="fnref:45" href="#fn:45"><sup>45</sup></a> The basal planes experience preferential oxygen adsorption and larger surface area facilitates electron transfer.<a class="footnote-ref" id="fnref:46" href="#fn:46"><sup>46</sup></a> In contrast, with ambient conditions, nanoplatelets of dimensions of four nm width and greater than 30 nm diameter have been experimentally synthesized with less cost and energy.<a class="footnote-ref" id="fnref:47" href="#fn:47"><sup>47</sup></a> Conversely, <a href="/facts/Localized_surface_plasmon_resonance/2eXxoTrH">localized surface plasmon resonances</a> observed in covellite <a href="/facts/Nanoparticle/k8kNxX4E">nanoparticles</a> have recently been linked to the <a href="/facts/Stoichiometry/I5p9cJzV">stoichiometry</a>-dependent <a href="/facts/Band_gap/IjIeh95l">band gap</a> key for nanocrystals.<a class="footnote-ref" id="fnref:48" href="#fn:48"><sup>48</sup></a><a class="footnote-ref" id="fnref:49" href="#fn:49"><sup>49</sup></a> Thus, future chemical sensing devices, electronics, and others instruments are being explored with the use of nanostructures with covellite CuS.<a class="footnote-ref" id="fnref:50" href="#fn:50"><sup>50</sup></a><a class="footnote-ref" id="fnref:51" href="#fn:51"><sup>51</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/List_of_minerals/4rMMcv2D">List of minerals</a></li> <li><a href="/facts/List_of_minerals_named_after_people/ElPKA5lI">List of minerals named after people</a></li></ul> <ul><li></li></ul> Wikimedia Commons has media related to Covellite. <ul><li></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Mindat.org <a href="http://www.mindat.org/min-1144.html" target="_blank">http://www.mindat.org/min-1144.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Mindat.org <a href="http://www.mindat.org/min-1144.html" target="_blank">http://www.mindat.org/min-1144.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Q. Ashton Acton (2012). Chlorine Compounds-Advances in Research and Application. ScholarlyMedia LLC. ISBN 9781481600040. OCLC 1024280169. <a href="9781481600040" target="_blank">9781481600040</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Mindat.org <a href="http://www.mindat.org/min-1144.html" target="_blank">http://www.mindat.org/min-1144.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Putnis, A.; Grace, J.; Cameron, W. E. (1977). "Blaubleibender covellite and its relationship to normal covellite". Contributions to Mineralogy and Petrology. 60 (2): 209–217. Bibcode:1977CoMP...60..209P. doi:10.1007/bf00372282. ISSN 0010-7999. S2CID 95661500. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Evans, Howard T.; Konnert, Judith A. (1976). "Crystal structure refinement of covellite". American Mineralogist. 61: 996–1000. <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Evans, Howard T.; Konnert, Judith A. (1976). "Crystal structure refinement of covellite". American Mineralogist. 61: 996–1000. <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Warner, Terence E. (2013). Synthesis, properties and mineralogy of important inorganic materials. Wiley. ISBN 9780470976234. OCLC 865009780. <a href="9780470976234" target="_blank">9780470976234</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Evans, Howard T.; Konnert, Judith A. (1976). "Crystal structure refinement of covellite". American Mineralogist. 61: 996–1000. <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Evans, Howard T.; Konnert, Judith A. (1976). "Crystal structure refinement of covellite". American Mineralogist. 61: 996–1000. <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Goble, Ronald J. (1985). The relationship between crystal structure, bonding and cell dimensions in the copper sulfides : supplementary unpublished material. OCLC 45557917. <a href="/wiki/OCLC_(identifier)" target="_blank">/wiki/OCLC_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Liang, W.; Whangbo, M.-H. (February 1993). "Conductivity anisotropy and structural phase transition in Covellite CuS". Solid State Communications. 85 (5): 405–408. Bibcode:1993SSCom..85..405L. doi:10.1016/0038-1098(93)90689-k. ISSN 0038-1098. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Liang, W.; Whangbo, M.-H. (February 1993). "Conductivity anisotropy and structural phase transition in Covellite CuS". Solid State Communications. 85 (5): 405–408. Bibcode:1993SSCom..85..405L. doi:10.1016/0038-1098(93)90689-k. ISSN 0038-1098. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Liang, W.; Whangbo, M.-H. (February 1993). "Conductivity anisotropy and structural phase transition in Covellite CuS". Solid State Communications. 85 (5): 405–408. Bibcode:1993SSCom..85..405L. doi:10.1016/0038-1098(93)90689-k. ISSN 0038-1098. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Evans, Howard T.; Konnert, Judith A. (1976). "Crystal structure refinement of covellite". American Mineralogist. 61: 996–1000. <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Liang, W.; Whangbo, M.-H. (February 1993). "Conductivity anisotropy and structural phase transition in Covellite CuS". Solid State Communications. 85 (5): 405–408. Bibcode:1993SSCom..85..405L. doi:10.1016/0038-1098(93)90689-k. ISSN 0038-1098. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Majzlan, Juraj; Kiefer, Stefan; Herrmann, Julia; Števko, Martin; Sejkora, Jiří; Chovan, Martin; Lánczos, Tomáš; Lazarov, Marina; Gerdes, Axel (June 2018). "Synergies in elemental mobility during weathering of tetrahedrite [(Cu,Fe,Zn)12(Sb,As)4S13]: Field observations, electron microscopy, isotopes of Cu, C, O, radiometric dating, and water geochemistry". Chemical Geology. 488: 1–20. Bibcode:2018ChGeo.488....1M. doi:10.1016/j.chemgeo.2018.04.021. ISSN 0009-2541. S2CID 135253715. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Warner, Terence E. (2013). Synthesis, properties and mineralogy of important inorganic materials. Wiley. ISBN 9780470976234. OCLC 865009780. <a href="9780470976234" target="_blank">9780470976234</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Simonescu, C.M., Teodorescu, V.S., Carp, O., Patron, L. and Capatina, C. (2007). "Thermal behaviour of CuS (covellite) obtained from copper–thiosulfate system". Journal of Thermal Analysis and Calorimetry. 88 (1): 71–76. doi:10.1007/s10973-006-8079-z. S2CID 94104147.{{cite journal}}: CS1 maint: multiple names: authors list (link) <a href="/wiki/Journal_of_Thermal_Analysis_and_Calorimetry" target="_blank">/wiki/Journal_of_Thermal_Analysis_and_Calorimetry</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Ghezelbash, Ali; Korgel, Brian A. (October 2005). "Nickel Sulfide and Copper Sulfide Nanocrystal Synthesis and Polymorphism". Langmuir. 21 (21): 9451–9456. doi:10.1021/la051196p. ISSN 0743-7463. PMID 16207021. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Ghezelbash, Ali; Korgel, Brian A. (October 2005). "Nickel Sulfide and Copper Sulfide Nanocrystal Synthesis and Polymorphism". Langmuir. 21 (21): 9451–9456. doi:10.1021/la051196p. ISSN 0743-7463. PMID 16207021. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Gramp, J.P.; Sasaki, K.; Bigham, J.M.; Karnachuck, O.V.; Tuovinen, O.H. (2006). "Formation of Covellite (CuS) Under Biological Sulfate-Reducing Conditions". Geomicrobiology Journal. 23 (8): 613–619. doi:10.1080/01490450600964383. S2CID 95152748. <a href="/w/index.php?title=Geomicrobiology_Journal&action=edit&redlink=1" target="_blank">/w/index.php?title=Geomicrobiology_Journal&action=edit&redlink=1</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Gramp, J.P.; Sasaki, K.; Bigham, J.M.; Karnachuck, O.V.; Tuovinen, O.H. (2006). "Formation of Covellite (CuS) Under Biological Sulfate-Reducing Conditions". Geomicrobiology Journal. 23 (8): 613–619. doi:10.1080/01490450600964383. S2CID 95152748. <a href="/w/index.php?title=Geomicrobiology_Journal&action=edit&redlink=1" target="_blank">/w/index.php?title=Geomicrobiology_Journal&action=edit&redlink=1</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Simonescu, C.M., Teodorescu, V.S., Carp, O., Patron, L. and Capatina, C. (2007). "Thermal behaviour of CuS (covellite) obtained from copper–thiosulfate system". Journal of Thermal Analysis and Calorimetry. 88 (1): 71–76. doi:10.1007/s10973-006-8079-z. 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