Hematite structure

Also: Hematite group / Corundum group.

It's a slightly nontrivial hexagonal crystal structure.

Highly abundant elements

• Al₂O₃ Aluminium(III)_oxide - leukosapphire - (Sapphire and Ruby are colored variants) - 2,072°C - 3.987g/ccm - Mohs 9 (defining compound)
• Ti₂O₃ Titanium(III)_oxide - tristarite - 2,130°C (decomposes) - 4.49g/ccm - metallic luster - semiconducting to metallic at 200°C - Mohs 8.5
• Fe₂O₃ iron(III)_oxide Hematite - 5.3g/ccm - Mohs 5.5 to 6.5
• – Mn₂O₃ only forms other different crystal structures with bigger unit cells (α-form, γ-form, ...) via thermodynamic means

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• FeTiO₃ Ilmenite - 4.72g/ccm - Mohs 5.5
• MgTiO₃ Geikielite - 4.4g/ccm - Mohs 5
• MnTiO₃ Pyrophanite - 4.75g/ccm - Mohs 5 to 6

More rare elements

• Cr₂O₃ eskolaite - 5.18g/ccm - Mohs 8 - metallic
• V₂O₃ karelianite (webmineral) - Mohs 8 to 9 - metallic luster
• Mn₂O₃ manganese-bixbyte - 4.95g/ccm - Mohs 6 to 6.5

Way too rare elements

• Sb₂O₃ antimony_trioxide senarmontite
• Sc₂O₃ kangite
• Y₂O₃ Yttriaite-(Y)
• Bi₂O₃ bismite bismuth(III)_oxide -- not the monoclinic one
• Tl₂O₃ avicennite - 8.9g/ccm - Mohs 2
• Sb₂O₃ valentinite - 5.76g/ccm - Mohs 2.5 to 3

Related

• Gemstone like compound
• Simple crystal structures of especial interest

External links

• Wikipediacategory: hematite group aka corundum group
• Short paper about the discovery of tistarite:
  "Tistarite, Ti2O3, a new refractory mineral from the Allende meteorite" (pdf)

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Corundum structure in 3D:

• at the materials project: [1]
• at www.mindat.org [2]
• at www.mineralienatlas.de [3]
• http://wwwchem.uwimona.edu.jm/courses/corundum.html – (good 3D view)
• corundum group minerals [4]