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Titanite, or sphene (from Ancient Greek σφηνώ (sphēnṓ) 'wedge'), [5] is a calcium titanium nesosilicate mineral, Ca Ti Si O 5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals including cerium and yttrium ; calcium may be partly replaced by thorium .
Rare-earth ore, shown with a United States penny for size comparison. A rare-earth mineral contains one or more rare-earth elements as major metal constituents. Rare-earth minerals are usually found in association with alkaline to peralkaline igneous magmas in pegmatites or with carbonatite intrusives.
The biotite crystals are 1–3 mm across, being more or less euhedral; but they contain small inclusions of titanite and magnetite, indicating that biotite crystallization began after them. The distinguishing feature of the Kuna Crest granodiorite is the presence of anhedral crystals of hornblende abounding in inclusions of the other minerals.
A pair of Titanites giganteus fossils at Wollaton Hall. Species of the genus Titanites can reach large sizes, with a diameter over 60 centimetres (2.0 ft) for Titanites giganteus and 90 centimetres (3.0 ft) for T. anguiformis. [2]
Brookite is the orthorhombic variant of titanium dioxide (TiO 2), which occurs in four known natural polymorphic forms (minerals with the same composition but different structure).
Calcium titanate is obtained as orthorhombic crystals, more specifically perovskite structure. [3] In this motif, the Ti(IV) centers are octahedral and the Ca 2+ centers occupy a cage of 12 oxygen centres.
Strontium titanate is an oxide of strontium and titanium with the chemical formula Sr Ti O 3.At room temperature, it is a centrosymmetric paraelectric material with a perovskite structure.
Other minerals known to undergo metamictisation include allanite, gadolinite, ekanite, thorite and titanite. Ekanite is almost invariably found completely metamict as thorium and uranium are part of its essential chemical composition. Metamict minerals can have their crystallinity and properties restored through prolonged annealing.