Titanite


Titanite



Titanite_from_Capelinha,_thumb|300pxTitanite or sphene is a calcium titanium nesosilicate mineral, CaTiSiO5. Trace impurities of iron and aluminium are invariably present. Also commonly present are rare earth metals including cerium and yttrium.

Nomenclature

The use of sphene as this mineral's name has been discredited by the International Mineralogical Association Commission on New Minerals and Mineral Names (CNMMN); titanite is the approved name (see [http://www.geo.vu.nl/users/ima-cnmmn/IMA-list.pdf CNMMN report] , p. 134). Sphene was the most commonly used name until the IMA decision, and is less confusing as titanates are a class of compound with the general formula XTiO3. The name sphene continues to be publishable in peer-reviewed scientific literature, e.g. a paper by Watson et al. was published in early 2008 in the journal Cotributions to Mineralogy and Petrology. Sphene persists as the informal name for titanite gemstones.

Physical properties

Titanite, which is named for its titanium content, occurs as translucent to transparent, reddish brown, gray, yellow, green, or red monoclinic crystals. These crystals are typically sphenoid (from the Greek "sphenos", meaning wedge) in habit and are often twinned. Possessing a subadamantine tending to slightly resinous lustre, titanite has a hardness of 5.5 and a weak cleavage. Its specific gravity varies between 3.52 and 3.54. Titanite's refractive index is 1.885-1.990 to 1.915-2.050 with a strong birefringence of 0.105 to 0.135 (biaxial positive). Transparent specimens are noted for their strong trichroism, the three colours presented being dependent on body colour. Owing to the quenching effect of iron, sphene exhibits no fluorescence under UV. Some titanite has been found to be metamict.

Titanite is a source of titanium dioxide, TiO2, used in pigments and is admired as a gemstone when suitably free of flaws.

Occurrence

Titanite occurs in metamorphic rocks such as gneiss and schists and also in granular limestones and granite. Source localites include: Pakistan, Italy, Russia, China, Brazil, Switzerland, Madagascar, the Tyrol (Austria), Canada (Renfrew County, Ontario) and the USA (California).

Use as a gemstone

As a gemstone, sphene is usually some shade of chartreuse and is highly prized for its exceptional dispersive power (0.051, B to G interval) which exceeds that of diamond. Unfortunately, brittleness and low hardness precludes appropriate use as a ring stone: sphene is more suited to pendants or brooches, or left unset as a collector's stone.

ee also

List of minerals

References

* [http://webmineral.com/data/Titanite.shtml Webmineral data]
* [http://www.mindat.org/min-4977.html Mindat.org]


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Look at other dictionaries:

  • Titanite — Catégorie IX : silicates[1] Titanite de Capelinha, au Brésil …   Wikipédia en Français

  • titanite — ● titanite nom féminin Synonyme de sphène. ● titanite (synonymes) nom féminin Synonymes : sphène titanite [titanit] n. f. ÉTYM. 1836; n. m., 1803; de titane. ❖ 1 Minéralogie. Silicate naturel de t …   Encyclopédie Universelle

  • Titanite — Ti tan*ite, n. [Cf. F. titanite; so called from containing titanic acid.] (Min.) See {Sphene}. [1913 Webster] …   The Collaborative International Dictionary of English

  • titanite — s. f. Silicato natural de titânio …   Dicionário da Língua Portuguesa

  • titanite — [tīt′ n īt΄] n. [Ger titanit: see TITANIUM & ITE1] SPHENE …   English World dictionary

  • titanite — /tuyt n uyt /, n. Mineral. sphene. [1790 1800; < G Titanit. See TITANIUM, ITE1] * * * ▪ mineral also called  sphene         titanium and calcium silicate mineral, CaTiSiO4(O,OH,F), that, in a crystallized or compact form, makes up a minor… …   Universalium

  • titanite — titanitas statusas T sritis chemija apibrėžtis Mineralas. formulė CaTi(SiO₄)(O,OH,F) atitikmenys: angl. sphene; titanite rus. сфен; титанит ryšiai: sinonimas – sfenas …   Chemijos terminų aiškinamasis žodynas

  • titanite — noun A mixed calcium and titanium neosilicate, CaTiSiO, once known as sphene …   Wiktionary

  • titanite — (ti ta ni t ) s. m. Terme de minéralogie. Synon. du titane silicéo calcaire de Haüy …   Dictionnaire de la Langue Française d'Émile Littré

  • titanite — pl.f. titaniti …   Dizionario dei sinonimi e contrari


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