Griffinite, Al2TiO5: A New Oxide Mineral from Inclusions in Corundum Xenocrysts from the Mount Carmel Area, Israel

Abstract

Griffinite (IMA 2021-110), ideally Al2TiO5, is a new mineral from inclusions in corundum xenocrysts from the Mount Carmel area, Israel. It occurs as subhedral crystals, ~1–4 μm in size, together with Zr-rich rutile within a corundum grain. In this study, a mean of eight electron probe microanalyses gave TiO2 44.41 (24), Al2O3 55.13 (18), FeO 0.47 (5), and MgO 0.37 (2), totaling 100.38 wt%, which corresponded, on the basis of a total of five oxygen atoms, to (Al1.97Mg0.02Fe0.01)Ti1.01O5. Electron back-scatter diffraction studies revealed that griffinite is orthorhombic and in the space group Cmcm, with a = 3.58 (2) Å, b = 9.44 (1) Å, c = 9.65 (1) Å, and V = 326 (2) Å3 with Z = 4. The six strongest calculated powder diffraction lines [d in Å (I/I0) (hkl)] are 3.347 (100) (110); 2.658 (90) (023); 4.720 (77) (020); 1.903 (57) (043); 1.790 (55) (200); and 1.688 (44) (134). In the crystal structure, Al3+ and Ti4+ are disordered into two distinct distorted octahedra, which form edge-sharing double chains. Griffinite is a high-temperature oxide mineral, formed in melt pockets in corundum-aggregate xenoliths derived from the upper mantle beneath Mount Carmel, Israel. The new mineral is named after William L. Griffin, a geologist at Macquarie University, Australia.

New Minerals from Inclusions in Corundum Xenocrysts from Mt. Carmel, Israel: Magnéliite, Ziroite, Sassite, Mizraite-(Ce) and Yeite

“…Carmel mount Corundum-18-1 is under the registration number MCMGPG-H2021-002. This corundum grain also hosts the type griffinite (Al 2 TiO 5 ; IMA 2021-110; [14]).…”

“…Yeite occurs with wenjiite (Ti5Si3) and zhiqinite (TiSi2) in Ti-Si alloy inclusions in corundum Grain 198c (Figure 13). Other inclusions in this corundum grain contain type griffinite (Al2TiO5) [14], rutile, baddeleyite, hibonite, osbornite, khamrabaevite, Ti,Al,Zroxide, zirconolite, and jingsuiite. Yeite occurs as irregular-subhedral crystals 1.2-3.5 µm in size.…”

“…Sassite (Ti 3+ 2 Ti 4+ O 5 ) is a new member of the pseudobrookite group, joining pseudobrookite (Fe 2 TiO 5 ), armalcolite [(Mg,Fe 2+ )Ti 2 O 5 ], and griffinite (Al 2 TiO 5 ; IMA 2021-110) [14]. Synthetic Ti 3 O 5 -pseudobrookite is well known (e.g., [31,32]).…”

“…The calculated density is 3.81 g•cm −3 using the empirical formula and the unit-cell volume estimated from the EBSD data. Sassite (Ti 3+ 2Ti 4+ O5) is a new member of the pseudobrookite group, joining pseudobrookite (Fe2TiO5), armalcolite [(Mg,Fe 2+ )Ti2O5], and griffinite (Al2TiO5; IMA 2021-110) [14]. Synthetic Ti3O5-pseudobrookite is well known (e.g., [31,32]).…”

“…All of them have been approved by the IMA-CNMNC (Commission on New Minerals, Nomenclature and Classification) as requested before naming and reporting the finding of a new mineral phase. Griffinite has been already published in detail [14]. Toledoite will be published in a separate paper.…”