Lorenzenite

(repeating unit)Na₂Ti₂[O₃|Si₂O₆]IMA symbolLrz^[1]Strunz classification9.DB.10Crystal systemOrthorhombicCrystal classDipyramidal (mmm)
H–M Symbol: (2/m 2/m 2/m)Space groupPbcnUnit cella = 8.71, b = 5.23
c = 14.48 [Å]; Z = 4IdentificationColorPale purple-brown, pale pink to mauve, brown to blackCrystal habitEquant, bladed, prismatic, to needlelike crystals; fibrous, felted, lamellar aggregatesCleavageDistinct/good on {010}FractureIrregular/unevenMohs scale hardness6LusterAdamantine, vitreous, sub-metallic, dullStreakWhite to pale brownDiaphaneityTransparent, opaqueSpecific gravity3.42 – 3.45Optical propertiesBiaxial (−)Refractive indexn_α = 1.910 – 1.950 n_β = 2.010 – 2.040 n_γ = 2.030 – 2.060Birefringenceδ = 0.120PleochroismWeak2V angleMeasured: 38° to 41°Ultraviolet fluorescencePale yellow to dull green under SW UVReferences^[2][3][4]

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.

It was first identified in 1897 in rock samples from Narsarsuk, Greenland.^[3] In 1947 it was discovered to be the same as the mineral ramsayite (now a synonym of lorenzenite), discovered in the 1920s in the Kola peninsula of Russia. It is also found in northern Canada.

It occurs in nepheline syenites and pegmatites in association with aegirine, nepheline, microcline, arfvedsonite, elpidite, loparite, eudialyte, astrophyllite, mangan-neptunite, lavenite, rinkite, apatite, titanite and ilmenite.^[2]

It was named in honor of Danish mineralogist Johannes Theodor Lorenzen (1855–1884).^[3]

References

Oxide minerals

Simple	Anatase Brookite Geikielite Rutile
Mixed	Aeschynite-(Y) Armalcolite Betafite Euxenite Freudenbergite Haggertyite Ilmenite Keilhauite Latrappite Perovskite Polycrase Zimbabweite Zirconolite Zirkelite

Silicate mineralsOther