Andalusite

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Andalusite
AndalousiteTyrol.jpg
Andalusite, Tyrol Austrick.
General
Category Nesosilicates
Formula
(repeatin unit)
Al2SiO5
Strunz clessification 09.AF.10
Creestal seestem orthorhombic
Space group 2/m 2/m 2/m - Dipyramidal
Unit cell a = 7.7980 Å b = 7.9031 Å c = 5.5566 Å; Z = 4
Identification
Colour Pink, violet, yellae, green, white, gray; in thin section, colourless tae pink or green
Creestal habit As euhedral crystals or columnar aggregates havin nearly square cross sections; fibrous compact tae massive
Twinnin On {101}, rare
Cleavage Guid on {110}, puir on {100}
Fractur uneven tae subconchoidal
Mohs scale haurdness 6.5 - 7.5
Skinkle Vitreous
Streak White
Diaphaneity Transparent tae nearly opaque wi inclusions
Speceefic gravity 3.17 (+/- .04)
Optical properties double refractive, biaxial negative; chiastolite haes anomalous aggregate reaction.[1]
Refractive index nα = 1.629 - 1.640 nβ = 1.633 - 1.644 nγ = 1.638 - 1.650
Birefringence δ = 0.009 - 0.010
Pleochroism Weak
2V angle 71 - 86°
Dispersion r < v strong
Ultraviolet fluorescence non-fluorescent
References [1][2][3][4]

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

References[eedit | eedit soorce]