Andalusite
Andalusite is an aluminium nesosilicate mineral wi the chemical formula Al2SiO5.
| Andalusite | |
|---|---|
 Andalusite | |
| 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] |
References
eedit- ↑ a b Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6
- ↑ http://rruff.geo.arizona.edu/doclib/hom/andalusite.pdf Handbook of Mineralogy
- ↑ http://www.mindat.org/show.php?id=217&ld=1&pho= Mindat.org
- ↑ http://webmineral.com/data/Andalusite.shtml Webmineral data