Editing Ilmenite (section)

== Structure and properties ==
Ilmenite is a heavy (specific gravity 4.7), moderately hard (Mohs hardness 5.6 to 6), opaque black mineral with a submetallic luster.<ref name=KleinHurlbut1993/> It is almost always massive, with thick tabular crystals being quite rare. It shows no discernible cleavage, breaking instead with a conchoidal to uneven fracture.<ref name=Sinkankas1964/>

Ilmenite crystallizes in the [[trigonal]] system with space group ''R''{{overline|3}}.<ref name=Nesse2000>{{cite book |last1=Nesse |first1=William D. |title=Introduction to mineralogy |date=2000 |publisher=Oxford University Press |location=New York |isbn=9780195106916 |pages=366–367}}</ref><ref name=HBM/> The ilmenite [[crystal structure]] consists of an ordered derivative of the [[corundum]] structure; in corundum all cations are identical but in ilmenite Fe<sup>2+</sup> and Ti<sup>4+</sup> ions occupy alternating layers perpendicular to the trigonal c axis.

Pure ilmenite is [[paramagnetic]] (showing only very weak attraction to a magnet), but ilmenite forms [[solid solution]]s with [[hematite]] that are weakly [[ferromagnetic]] and so are noticeably attracted to a magnet. Natural deposits of ilmenite usually contain intergrown or exsolved [[magnetite]] that also contribute to its ferromagnetism.<ref name=KleinHurlbut1993>{{cite book |last1=Klein |first1=Cornelis |last2=Hurlbut |first2=Cornelius S. Jr. |title=Manual of mineralogy : (after James D. Dana) |date=1993 |publisher=Wiley |location=New York |isbn=047157452X |edition=21st |pages=380–381}}</ref>

Ilmenite is distinguished from hematite by its less intensely black color and duller appearance and its black [[Streak (mineralogy)|streak]], and from magnetite by its weaker magnetism.<ref name=Sinkankas1964>{{cite book |last1=Sinkankas |first1=John |title=Mineralogy for amateurs. |date=1964 |publisher=Van Nostrand |location=Princeton, N.J. |isbn=0442276249 |pages=328–329}}</ref><ref name=KleinHurlbut1993/>

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Image:Ilmenite.GIF|Crystal structure of ilmenite
File:Ilmenite-65675.jpg|Ilmenite from Froland, Aust-Agder, Norway; 4.1 × 4.1 × 3.8&nbsp;cm
File:Ilmenite and hematite under normal light.jpg|Ilmenite and hematite under normal light
File:Ilmenite and hematite under polarized light.jpg|Ilmenite and hematite under polarized light
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