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Doubly terminated crystal of Lorenzenite, 2.5 cm tip to tip, from Lovozero Massif, Kola Peninsula, Russia
Category Silicate mineral
(repeating unit)
Strunz classification 9.DB.10
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H–M Symbol: (2/m 2/m 2/m)
Space group 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
Crystal habit Equant, bladed, prismatic, to needlelike crystals; fibrous, felted, lamellar aggregates
Cleavage Distinct/good on {010}
Fracture Irregular/uneven
Mohs scale hardness 6
Luster Adamantine, vitreous, sub-metallic, dull
Streak White to pale brown
Diaphaneity Transparent, opaque
Specific gravity 3.42 - 3.45
Optical properties Biaxial (-)
Refractive index nα = 1.910 - 1.950 nβ = 2.010 - 2.040 nγ = 2.030 - 2.060
Birefringence δ = 0.120
Pleochroism Weak
2V angle Measured: 38° to 41°
Ultraviolet fluorescence Pale yellow to dull green under SW UV
References [1][2][3]

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.[2] 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.[1]

It was named in honor of Danish mineralogist Johannes Theodor Lorenzen (1855–1884).[2]