Andalusite

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Andalusite
AndalousiteTyrol.jpg
Andalusite, Tyrol Austrick.
General
CategoryNesosilicates
Formula
(repeatin unit)
Al2SiO5
Strunz clessification09.AF.10
Creestal seestemorthorhombic
Space group2/m 2/m 2/m - Dipyramidal
Unit cella = 7.7980 Å b = 7.9031 Å c = 5.5566 Å; Z = 4
Identification
ColourPink, violet, yellae, green, white, gray; in thin section, colourless tae pink or green
Creestal habitAs euhedral crystals or columnar aggregates havin nearly square cross sections; fibrous compact tae massive
TwinninOn {101}, rare
CleavageGuid on {110}, puir on {100}
Fracturuneven tae subconchoidal
Mohs scale haurdness6.5 - 7.5
SkinkleVitreous
StreakWhite
DiaphaneityTransparent tae nearly opaque wi inclusions
Speceefic gravity3.17 (+/- .04)
Optical propertiesdouble refractive, biaxial negative; chiastolite haes anomalous aggregate reaction.[1]
Refractive indexnα = 1.629 - 1.640 nβ = 1.633 - 1.644 nγ = 1.638 - 1.650
Birefringenceδ = 0.009 - 0.010
PleochroismWeak
2V angle71 - 86°
Dispersionr < v strong
Ultraviolet fluorescencenon-fluorescent
References[1][2][3][4]

Andalusite is an aluminium nesosilicate meeneral wi the chemical formula Al2SiO5.

References[eedit | eedit soorce]