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Kyanite [Al2SiO5]
Structure Triclinic
Space Group P-1
(No. 2)
a=7.1262 Å, b=7.8520 Å, c=5.5724 Å
a=89.99, b=101.11, g=106.03
Z=4
Atomic Positional Parameters
Al1 2i 0.3254 0.7040 0.4582
Al2 2i 0.2974 0.6989 0.9505
Al3 2i 0.0998 0.3862 0.6403
Al4 2i 0.1120 0.9175 0.1649
Si1 2i 0.2962 0.0649 0.7066
Si2 2i 0.2910 0.3317 0.1892
O1 2i 0.1095 0.1468 0.1288
O2 2i 0.1230 0.6856 0.1812
O3 2i 0.2747 0.4545 0.9547
O4 2i 0.2831 0.9354 0.9353
O5 2i 0.1084 0.1520 0.6669
O6 2i 0.1219 0.6307 0.6389
O7 2i 0.2822 0.4453 0.4288
O8 2i 0.2915 0.9467 0.4659
O9 2i 0.5008 0.2749 0.2440
O10 2i 0.5015 0.2312 0.7553
Reference
JK Winter and S Ghose (1979) American Mineralogist, 64, 573-586
Mineral Chemistry
Kyanite is one of the three aluminium silicate polymorphs, the other two being andalusite and sillimanite. Formed in metamorphosed aluminous rocks at moderate temperatures and moderate to high pressures, kyanite may be associated with garnet, corundum and staurolite, which has a crystal structure very closely related to kyanite. In kyanite, aluminiums are coordinated by six oxygens, silicons by four. The oxygen atoms are arranged in a close-packed fashion.
The CHIME figure shows aluminiums as grey spheres, silicons as yellow spheres, and oxygens as red spheres.