lorenzenite

{{Infobox mineral | name = Lorenzenite | boxwidth = | boxbgcolor = | image = Lorenzenite-mrz179b.jpg | imagesize = | alt = | caption = Doubly terminated crystal of Lorenzenite, 2.5 cm tip to tip, from Lovozero Massif, Kola Peninsula, Russia | category = Silicate mineral | formula = Na2Ti2[O3|Si2O6] | IMAsymbol = Lrz | molweight = | strunz = 9.DB.10 | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H–M Symbol: (2/m 2/m 2/m) | symmetry = Pbcn | unit cell = a = 8.71, b = 5.23 c = 14.48 [Å]; Z = 4 | color = Pale purple-brown, pale pink to mauve, brown to black | colour = | habit = Equant, bladed, prismatic, to needlelike crystals; fibrous, felted, lamellar aggregates | twinning = | cleavage = Distinct/good on {010} | fracture = Irregular/uneven | tenacity = | mohs = 6 | luster = Adamantine, vitreous, sub-metallic, dull | streak = White to pale brown | diaphaneity = Transparent, opaque | gravity = 3.42 – 3.45 | density = | polish = | opticalprop = Biaxial (−) | refractive = nα = 1.910 – 1.950 nβ = 2.010 – 2.040 nγ = 2.030 – 2.060 | birefringence = δ = 0.120 | pleochroism = Weak | 2V = Measured: 38° to 41° | dispersion = | extinction = | length fast/slow = | fluorescence = Pale yellow to dull green under SW UV | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }}

Lorenzenite is a rare sodium titanium silicate mineral with the formula Na2Ti2Si2O9 It is an orthorhombic mineral, variously found as colorless, grey, pinkish, or brown crystals.