titanite

{{Infobox mineral | name = Titanite (Sphene) | category = Nesosilicate | boxwidth = | boxbgcolor = #5d2613 | boxtextcolor = #FFFFFF | image = Titanite crystals on Amphibole - Ochtendung, Eifel, Germany.jpg | imagesize = 260px | caption = Titanite crystals on amphibole (image width 2 mm) | formula = | IMAsymbol = Ttn | strunz = 9.AG.15 | system = Monoclinic | class = Prismatic (2/m) (same H–M symbol) | symmetry = P21/a | unit cell = a = 7.057 Å, b = 8.707 Å c = 6.555 Å; β = 113.81°; Z = 4 | colour = Reddish brown, brown, gray, black, yellow, green, or red, colourless | habit = Flattened wedge-shaped crystals, also massive | twinning = Contact and penetration on {100}, lamellar on {221} | cleavage = Distinct on [110], parting on {221} | fracture = Sub-conchoidal | tenacity = | mohs = 5–5.5 | luster = Sub-adamantine tending to slightly resinous | streak = Reddish white | diaphaneity = Translucent to transparent | gravity = 3.48–3.60 | density = | polish = | opticalprop = Biaxial (+); very high relief | refractive = nα = 1.843–1.950nβ = 1.870–2.034 nγ = 1.943–2.110 | birefringence = δ = 0.100–0.160 | pleochroism = Strong: X = nearly colorless; Y = yellow to green; Z = red to yellow-orange | 2V = 17–40° (measured) | dispersion = r > v strong | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = 25px Radioactive – may be metamict | alteration = | references = }} thumb|150px|Titanite crystal model

Titanite, or sphene (), is a calcium titanium nesosilicate mineral, CaTiSiO5. 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.