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Huttonite
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<h2 id="occurrence">Occurrence</h2> <p>Huttonite was first described in 1950 from beach sand and <a href="/facts/Fluvio-glacial/rMKQU1Tv">fluvio-glacial</a> deposits in <a href="/facts/Westland_District/cqT0r0UC">South Westland</a>, New Zealand, where it was found as <a href="/facts/Euhedral/mPvgfKGz">anhedral</a> grains of no more than 0.2 mm maximum dimension. It is most prevalent in the sand at <a href="/facts/Gillespies_Beach/cAxprHAp">Gillespies Beach</a>, near <a href="/facts/Fox_Glacier/zsQYFcJw">Fox Glacier</a>,<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a><a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> which is the <a href="/facts/Type_locality_(geology)/ky6QjASt">type location</a>, where it is accompanied by <a href="/facts/Scheelite/Te4N0qKN">scheelite</a>, <a href="/facts/Cassiterite/d4hzR7LB">cassiterite</a>, <a href="/facts/Zircon/84APfbLt">zircon</a>, uranothorite, <a href="/facts/Ilmenite/fh2eXgpo">ilmenite</a> and <a href="/facts/Gold/1znknojp">gold</a>. It was found at a further six nearby locations in less plentiful amounts.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Huttonite was extracted from the sands by first fractionating in <a href="/facts/Iodomethane/uUKdue80">iodomethane</a> and then electromagnetically. Pure samples were subsequently obtained by handpicking huttonite grains under a microscope. This was accomplished either in the presence of short wave (2540 Å) <a href="/facts/Fluorescent/qsJVT2qP">fluorescent</a> light, where the dull white fluorescence distinguishes it from scheelite (fluoresces blue) and zircon (fluoresces yellow), or by first boiling the impure sample in <a href="/facts/Hydrochloric_acid/HqItJlUT">hydrochloric acid</a> to induce an oxide surface on scheelite and permitting handpicking under visible light.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p><p>Hutton suggested the huttonite contained in the beach sand and fluvio-glacial deposits originated from <a href="/facts/Otago/9kReoHt6">Otago</a> <a href="/facts/Schist/jHBjtEQw">schists</a> or <a href="/facts/Pegmatite/qW5BUXPg">pegmatitic veins</a> in the <a href="/facts/Southern_Alps_(New_Zealand)/FjQQURuc">Southern Alps</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>In addition to <a href="/facts/New_Zealand/4mpSlJdg">New Zealand</a>, huttonite has been found in <a href="/facts/Granitic/WdvRm9Ye">granitic</a> <a href="/facts/Pegmatite/qW5BUXPg">pegmatites</a> of <a href="/facts/Bogatynia/dgl0qtB7">Bogatynia, Poland</a>,<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> where it associated with <a href="/facts/Cheralite/IyR9UaJT">cheralite</a>, thorogummite, and ningyoite; and in <a href="/facts/Nepheline_syenite/An1mWGNU">nepheline syenites</a> of <a href="/facts/Brevik%2c_Norway/h12pE1TV">Brevik, Norway</a>.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <h2 id="physical-properties">Physical properties</h2> <p>Huttonite typically occurs as anhedral grains with no external crystal faces. It is usually colorless but also appears in colors; such as cream and pale yellow. It has a white streak. It has a hardness of 4.5 and exhibits distinct cleavage parallel to the c-axis [001] and an indistinct cleavage along the a-axis [100]. </p> <h2 id="structure">Structure</h2> <p>Huttonite is a <a href="/facts/Thorium/ysdWH470">thorium</a> <a href="/facts/Nesosilicate/WclrQW2I">nesosilicate</a> with the chemical formula ThSiO4. It is composed (by weight) of 71.59% thorium, 19.74% oxygen, and 8.67% silicon. Huttonite is found very close to its ideal <a href="/facts/Stoichiometry/I5p9cJzV">stoichiometric</a> composition, with impurities contributing less than 7% <a href="/facts/Mole_fraction/nW4EepmJ">mole fraction</a>. The most significant impurities to be observed are <a href="/facts/Uranium_dioxide/BqI7GJDq">UO2</a> and <a href="/facts/P2O5/GKTSUNqS">P2O5</a>.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <p>Huttonite crystallizes in the <a href="/facts/Monoclinic/5PCwXvzX">monoclinic</a> system with <a href="/facts/Space_group/2XQx0J7M">space group</a> P21/<i>n</i>. The unit cell contains four ThSiO4 units, and has dimensions <i>a</i> = 6.784 ± 0.002Å, <i>b</i> = 6.974 ± 0.003Å, <i>c</i> = 6.500 ± 0.003Å, and inter–axis angle <i>β</i> = 104.92 ± 0.03o. The structure is that of a <a href="/facts/Nesosilicate/WclrQW2I">nesosilicate</a> — discrete SiO42− tetrahedra coordinating thorium ions. Each thorium has <a href="/facts/Coordination_number/mf48hsoX">coordination number</a> nine. Axially, four oxygen atoms, representing the edges of two SiO4 monomers on opposite sides of the thorium atom, form a (–SiO4–Th–) chain parallel to the <i>c</i> axis. Equatorially, five nearly planar oxygen atoms representing vertices of distinct silicate tetrahedra coordinate each thorium. The lengths of the axial Th–O bonds are 2.43 Å, 2.51 Å, 2.52 Å, 2.81 Å, and of the equatorial bonds, 2.40 Å, 2.41 Å, 2.41 Å, 2.50 Å, and 2.58 Å. The Si–O bonds are nearly equal, with lengths 1.58 Å, 1.62 Å, 1.63 Å, and 1.64 Å.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p><p>Huttonite is isostructural with <a href="/facts/Monazite/an71GkIH">monazite</a>. Substitution of the <a href="/facts/Rare-earth_element/PQSUQumk">rare-earth elements</a> and phosphorus of monazite with thorium and silicon of huttonite can occur to generates a <a href="/facts/Solid_solution/Mla7z8dc">solid solution</a>. At the huttonite end-member, continuous rare-earth substitution of thorium of up to 20% by weight has been observed. Thorium substitution in monazite has been observed up to 27% by weight. Substitution of PO4 for SiO4 also occurs associated with the introduction of <a href="/facts/Fluoride/LpqNMzwa">fluoride</a>, <a href="/facts/Hydroxide/zW0wxpWD">hydroxide</a>, and metal ions.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>Huttonite is <a href="/facts/Polymorphism_(materials_science)/bu2tqsB9">dimorphic</a> with <a href="/facts/Thorite/R8V3QAob">thorite</a>. Thorite crystallizes in a higher symmetry and lower density <a href="/facts/Tetragonal/12Aop255">tetragonal</a> form in which the thorium atoms coordinate to one less oxygen atom in an octahedral arrangement. Thorite is stable at lower temperatures than huttonite; at 1 atmosphere, the thorite–huttonite phase transition occurs between 1210 and 1225 °C. With increasing pressure the transition temperature increases. This relatively high transition temperature is thought to explain the relative rarity of huttonite on the Earth's crust.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> Unlike thorite, huttonite is not affected by <a href="/facts/Metamictization/60dEABID">metamictization</a>. </p> <h2 id="external-links">External links</h2> <ul><li><a href="http://rruff.geo.arizona.edu/AMS/minerals/Huttonite">American Mineralogist Crystal Structure Database entry</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Pabst, A. (1950). "Monoclinic Thorium Silicate". Nature. 166 (4212): 157. Bibcode:1950Natur.166..157P. doi:10.1038/166157a0. PMID 15439198. S2CID 4200225. <a href="/wiki/Adolf_Pabst" target="_blank">/wiki/Adolf_Pabst</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Pabst, A. (1950). "Monoclinic Thorium Silicate". Nature. 166 (4212): 157. Bibcode:1950Natur.166..157P. doi:10.1038/166157a0. PMID 15439198. S2CID 4200225. <a href="/wiki/Adolf_Pabst" target="_blank">/wiki/Adolf_Pabst</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Pabst, A.; C. Osborne Hutton (1951). "Huttonite, a new monoclinic thorium silicate" (PDF). Am. Mineral. 36: 60–69. <a href="http://www.minsocam.org/ammin/AM36/AM36_60.pdf" target="_blank">http://www.minsocam.org/ammin/AM36/AM36_60.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Hutton, C. Osborne (1951). "Occurrence, optical properties and chemical composition of huttonite" (PDF). Am. Mineral. 36 (1): 66–69. <a href="http://www.minsocam.org/ammin/AM36/AM36_66.pdf" target="_blank">http://www.minsocam.org/ammin/AM36/AM36_66.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Hutton, C. Osborne (1951). "Occurrence, optical properties and chemical composition of huttonite" (PDF). Am. Mineral. 36 (1): 66–69. <a href="http://www.minsocam.org/ammin/AM36/AM36_66.pdf" target="_blank">http://www.minsocam.org/ammin/AM36/AM36_66.pdf</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Hutton, C. Osborne (1951). "Occurrence, optical properties and chemical composition of huttonite" (PDF). Am. Mineral. 36 (1): 66–69. <a href="http://www.minsocam.org/ammin/AM36/AM36_66.pdf" target="_blank">http://www.minsocam.org/ammin/AM36/AM36_66.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Kucha, H (1980). "Continuity in the monazite–huttonite series". Mineralogical Magazine. 43 (332): 1031–1034. Bibcode:1980MinM...43.1031K. doi:10.1180/minmag.1980.043.332.12. S2CID 54584872. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Meldrum, A., Boatner, L.A., Zinkle, S.J., Wang, S.-X., Wang, L.-M., and Ewing, R.C. (1999). "Effects of dose rate and temperature on the crystalline–to–metamict transformation in the ABO4 orthosilicates". Canadian Mineralogist. 37: 207–221.{{cite journal}}: CS1 maint: multiple names: authors list (link) <a href="/wiki/Template:Cite_journal" target="_blank">/wiki/Template:Cite_journal</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Förster H. J., Harlov D. E., Milke R., H.-J.; Harlov, D. E.; Milke, R. (2000). "Composition and Th –U –total Pb ages of huttonite and thorite from Gillespie's Beach,. South Island, New Zealand". The Canadian Mineralogist. 38 (3): 675–684. Bibcode:2000CaMin..38..675F. CiteSeerX 10.1.1.579.7465. doi:10.2113/gscanmin.38.3.675.{{cite journal}}: CS1 maint: multiple names: authors list (link) <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Taylor, Mark; Ewing, R. C. (1978). "The Crystal Structures of the ThSiO4 Polymorphs: Huttonite and Thorite". Acta Crystallogr. B. 34 (4): 1074–1079. Bibcode:1978AcCrB..34.1074T. doi:10.1107/S0567740878004951. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Kucha, Henryk (1980). "Continuity in the monazite–huttonite series". Mineralogical Magazine. 43 (332): 1031–1034. Bibcode:1980MinM...43.1031K. doi:10.1180/minmag.1980.043.332.12. S2CID 54584872. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Speer, J. A. (1980). "The actinide orthosilicates". Reviews in Mineralogy and Geochemistry. 5 (1): 113–135. <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> </ol>