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Brookite
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<h2 id="unit-cell">Unit cell</h2> <p>Brookite belongs to the <a href="/facts/Orthorhombic_crystal_system/3zo4F8P0">orthorhombic</a> dipyramidal <a href="/facts/Crystallographic_point_group/43NqYrf0">crystal class</a> 2/m 2/m 2/m (also designated mmm). The <a href="/facts/Space_group/2XQx0J7M">space group</a> is Pcab and the <a href="/facts/Crystal_structure/bJ4bCeHd">unit cell</a> parameters are a = 5.4558 Å, b = 9.1819 Å and c = 5.1429 Å. The <a href="/facts/Chemical_formula/hghUtthl">formula</a> is TiO2, with 8 formula units per unit cell.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a><a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h2 id="structure">Structure</h2> <p>The brookite structure is built up of distorted <a href="/facts/Octahedron/G38q92xW">octahedra</a> with a <a href="/facts/Titanium/53ArnDoy">titanium</a> <a href="/facts/Ion/3bePpDna">ion</a> at the center and <a href="/facts/Oxygen/acyn6o8r">oxygen</a> ions at each of the six vertices. Each octahedron shares three edges with adjoining octahedra, forming an <a href="/facts/Orthorhombic_crystal_system/3zo4F8P0">orthorhombic</a> structure.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <h2 id="appearance">Appearance</h2> <p>Brookite crystals are typically tabular, elongated and <a href="/facts/Striation_(geology)/PRXvx9We">striated</a> parallel to their length. They may also be <a href="/facts/Pyramid_(geometry)/fCXRgFwu">pyramidal</a>, pseudo-<a href="/facts/Hexagon/DPzuCzWE">hexagonal</a> or <a href="/facts/Prism_(geometry)/baIRRkCy">prismatic</a>.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> Brookite and <a href="/facts/Rutile/qwJH5ElN">rutile</a> may grow together in an <a href="/facts/Epitaxial/etjSn1D3">epitaxial</a> relationship.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p>Brookite is usually brown in color, sometimes yellowish or reddish brown, or even black. Beautiful, deep red crystals (seen above-right) similar to <a href="/facts/Pyrope/A0fdIhrs">pyrope</a> and <a href="/facts/Almandine/4VxjwYv2">almandite</a> garnet are also known. Brookite displays a submetallic <a href="/facts/Lustre_(mineralogy)/TCobwMGC">luster</a>. It is opaque to translucent, transparent in thin fragments and yellowish brown to dark brown in transmitted light.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a><a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> </p> <h2 id="optical-properties">Optical properties</h2> <p>Brookite is <a href="/facts/Birefringence/J4lLuR3a">doubly refracting</a>, as are all orthorhombic minerals, and it is <a href="/facts/Birefringence/J4lLuR3a">biaxial (+)</a>. <a href="/facts/Refractive_Index/yjkzvgeE">Refractive indices</a> are very high, above 2.5, which is even higher than <a href="/facts/Diamond/IBUdnd1y">diamond</a> at 2.42. For comparison, ordinary window glass has a refractive index of about 1.5. </p><p>Brookite exhibits very weak <a href="/facts/Pleochroism/EJJclyzk">pleochroism</a>, yellowish, reddish and orange to brown.<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a><a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> It is neither <a href="/facts/Fluorescence/qsJVT2qP">fluorescent</a> nor <a href="/facts/Radioactive_decay/Ya6FVjt4">radioactive</a>.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> </p> <h2 id="physical-properties">Physical properties</h2> <p>Brookite is a <a href="/facts/Brittleness/cn27H2vg">brittle</a> mineral, with a subconchoidal to irregular <a href="/facts/Fracture_(mineralogy)/Xzc4yDjy">fracture</a> and poor <a href="/facts/Cleavage_(crystal)/p4YHe01X">cleavage</a> in one direction parallel to the <i>c</i> <a href="/facts/Crystal_structure/bJ4bCeHd">crystal axis</a> and traces of cleavage in a direction perpendicular to both the <i>a</i> and the <i>b</i> crystal axes.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> <a href="/facts/Crystal_twinning/7xU6CKfR">Twinning</a> is uncertain.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> The mineral has a <a href="/facts/Mohs_hardness/wXBMcVIm">Mohs hardness</a> of 5+1⁄2 to 6, between <a href="/facts/Apatite/f5tYvl1n">apatite</a> and <a href="/facts/Feldspar/DVvFnfA9">feldspar</a>. This is the same hardness as anatase and a little less than that of rutile (6 to 6+1⁄2). The <a href="/facts/Specific_gravity/ySquGd2x">specific gravity</a> is 4.08 to 4.18, between that of anatase at 3.9 and rutile at 4.2.<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a><a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a> </p> <h2 id="occurrence-and-associations">Occurrence and associations</h2> <p>Brookite is an accessory mineral in <a href="/facts/Vein_(geology)/TyETstxF">alpine veins</a> in <a href="/facts/Gneiss/rUJYgBHu">gneiss</a> and <a href="/facts/Schist/jHBjtEQw">schist</a>; it is also a common <a href="/facts/Detritus_(geology)/UBsjHYRH">detrital mineral</a>.<a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a><a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a> Associated minerals include its <a href="/facts/Polymorphism_(materials_science)/bu2tqsB9">polymorphs</a> <a href="/facts/Anatase/wD932gCW">anatase</a> and <a href="/facts/Rutile/qwJH5ElN">rutile</a>, and also <a href="/facts/Titanite/h9l6Xqt8">titanite</a>, <a href="/facts/Orthoclase/xTjjm0gP">orthoclase</a>, <a href="/facts/Quartz/4n86tE2G">quartz</a>, <a href="/facts/Hematite/716YBzGr">hematite</a>, <a href="/facts/Calcite/gKMHYQJo">calcite</a>, <a href="/facts/Chlorite_group/1jzSNrwH">chlorite</a> and <a href="/facts/Muscovite/jMq51dyg">muscovite</a>.<a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> </p><p>The <a href="/facts/Type_locality_(geology)/ky6QjASt">type locality</a> is Twll Maen Grisial, Fron Olau, <a href="/facts/Prenteg/jIQNTFKo">Prenteg</a>, <a href="/facts/Gwynedd/LtCLSGgy">Gwynedd</a>, <a href="/facts/Wales/xa3W6PHH">Wales</a>.<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> In 2004, brookite crystals were found in the <a href="/facts/Kharan_District/L7eVjUnt">Kharan</a>, in <a href="/facts/Balochistan/gwrWvcJE">Balochistan</a>, Pakistan.<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</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_recognized_by_the_International_Mineralogical_Association/X8HhIayP">List of minerals recognized by the International Mineralogical Association</a></li> <li><a href="/facts/List_of_minerals_named_after_people/ElPKA5lI">List of minerals named after people</a></li></ul> <h2 id="external-links">External links</h2> <a href="/facts/Wikisource/TrMdylNf">Wikisource</a> has the text of the <a href="/facts/Encyclop%25C3%25A6dia_Britannica_Eleventh_Edition/mPElbCRY">1911 <i>Encyclopædia Britannica</i></a> article "Brookite". Wikimedia Commons has media related to Brookite. <ul><li><a href="https://web.archive.org/web/20110515111256/http://cst-www.nrl.navy.mil/lattice/struk/c21.html">Brookite structure </a></li> <li><a href="http://ruby.colorado.edu/~smyth/min/tio2.html">Crystal structures of rutile, anatase and brookite</a> <a href="https://web.archive.org/web/20090131093137/http://ruby.colorado.edu/~smyth/min/tio2.html">Archived</a> 2009-01-31 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a></li> <li><a href="http://rruff.geo.arizona.edu/AMS/viewJmol.php?id=05208">JMol</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Di Paola, A; Addamo, M.; Bellardita, M.; Cazzanelli, E.; Palmisano, L. (2007). "Preparation of photocatalytic brookite thin films". Thin Solid Films. 515 (7–8): 3527–3529. Bibcode:2007TSF...515.3527D. doi:10.1016/j.tsf.2006.10.114. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Anatase and Brookite Archived 2012-03-17 at the Wayback Machine. Wikis.lib.ncsu.edu (2007-05-08). Retrieved on 2011-10-14. <a href="http://wikis.lib.ncsu.edu/index.php/Anatase_and_Brookite" target="_blank">http://wikis.lib.ncsu.edu/index.php/Anatase_and_Brookite</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Brookite. Webmineral.com. Retrieved on 2011-10-14. <a href="http://www.webmineral.com/data/Brookite.shtml" target="_blank">http://www.webmineral.com/data/Brookite.shtml</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Arkansite on Mindat <a href="https://www.mindat.org/min-7844.html" target="_blank">https://www.mindat.org/min-7844.html</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Brookite (Titanium Oxide). Galleries.com. Retrieved on 2011-10-14. <a href="http://www.galleries.com/minerals/oxides/brookite/brookite.htm" target="_blank">http://www.galleries.com/minerals/oxides/brookite/brookite.htm</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Brookite. Webmineral.com. Retrieved on 2011-10-14. <a href="http://www.webmineral.com/data/Brookite.shtml" target="_blank">http://www.webmineral.com/data/Brookite.shtml</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Brookite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-14. <a href="http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf" target="_blank">http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>The Crystal Structure of Brookite. paulingblog.wordpress.com. 12 January 2010 <a href="http://paulingblog.wordpress.com/2010/01/12/the-crystal-structure-of-brookite" target="_blank">http://paulingblog.wordpress.com/2010/01/12/the-crystal-structure-of-brookite</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Brookite. Webmineral.com. Retrieved on 2011-10-14. <a href="http://www.webmineral.com/data/Brookite.shtml" target="_blank">http://www.webmineral.com/data/Brookite.shtml</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Brookite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-14. <a href="http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf" target="_blank">http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Brookite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-14. <a href="http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf" target="_blank">http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Brookite. Webmineral.com. Retrieved on 2011-10-14. <a href="http://www.webmineral.com/data/Brookite.shtml" target="_blank">http://www.webmineral.com/data/Brookite.shtml</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Brookite. Webmineral.com. Retrieved on 2011-10-14. <a href="http://www.webmineral.com/data/Brookite.shtml" target="_blank">http://www.webmineral.com/data/Brookite.shtml</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Brookite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-14. <a href="http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf" target="_blank">http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Brookite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-14. <a href="http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf" target="_blank">http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Brookite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-14. <a href="http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf" target="_blank">http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Brookite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-14. <a href="http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf" target="_blank">http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>Brookite. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-14. <a href="http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf" target="_blank">http://rruff.geo.arizona.edu/doclib/hom/brookite.pdf</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Brookite. Mindat.org (2011-09-17). Retrieved on 2011-10-14. <a href="http://www.mindat.org/min-787.html" target="_blank">http://www.mindat.org/min-787.html</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> </ol>