Kornerupine: Its Crystal Structure

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Science  02 Feb 1968:
Vol. 159, Issue 3814, pp. 524-526
DOI: 10.1126/science.159.3814.524


Three-dimensional analysis of the crystal structure of kornerupine reveals the crystallochemical formula MgVI2MgVIAlVI6[Si2O7] [(Al,Si)2 SiO10]O4(OH), with four formula units in the structure cell of a = 16.100 (2) Å, b = 13.767(2) Å, c = 6.735(2) Å; space group, Cmcm. The unusual crystal structure includes walls of Al-O edge and corner-sharing octahedra, and chains of alternating Mg-O and Al-O octahedra fused to the walls by further edge-sharing to form dense slabs. These slabs are held together by [Si2O7] corner-sharing tetrahedral pairs and [(Al,Si)2SiO10] corner-sharing tetrahedral triplets.