Chemistry:Lorenzenite

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Lorenzenite
Lorenzenite-mrz179b.jpg
Doubly terminated crystal of Lorenzenite, 2.5 cm tip to tip, from Lovozero Massif, Kola Peninsula, Russia
General
CategorySilicate mineral
Formula
(repeating unit)
Na2Ti2[O3|Si2O6]
Strunz classification9.DB.10
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H–M Symbol: (2/m 2/m 2/m)
Space groupPbcn
Unit cella = 8.71, b = 5.23
c = 14.48 [Å]; Z = 4
Identification
ColorPale purple-brown, pale pink to mauve, brown to black
Crystal habitEquant, bladed, prismatic, to needlelike crystals; fibrous, felted, lamellar aggregates
CleavageDistinct/good on {010}
FractureIrregular/uneven
Mohs scale hardness6
|re|er}}Adamantine, vitreous, sub-metallic, dull
StreakWhite to pale brown
DiaphaneityTransparent, opaque
Specific gravity3.42 - 3.45
Optical propertiesBiaxial (-)
Refractive indexnα = 1.910 - 1.950 nβ = 2.010 - 2.040 nγ = 2.030 - 2.060
Birefringenceδ = 0.120
PleochroismWeak
2V angleMeasured: 38° to 41°
Ultraviolet fluorescencePale 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]

References