Crystalline Systems

Written by Alain Darbellay GGGems

2004 All rights reserved. 7 systems of crystallization: There are 32 possibilities of combinations ofrepparttar elements of symmetry (axis of rotation, symmetry plane, centers combined inversion and operations). Sincerepparttar 109294 discovery ofrepparttar 109295 crystals reticular structure, one could show by calculation that to these 32 classes which relate torepparttar 109296 shapes ofrepparttar 109297 crystals, correspond 230 types of network. One immediately realizesrepparttar 109298 complexity ofrepparttar 109299 reasoning which should be made to know allrepparttar 109300 possible combinations. The 32 classes are grouped in 7 systems. Here arerepparttar 109301 figures. CUBIC SYSTEM QUADRATIC SYSTEM HEXAGONAL SYSTEM Go to Garnet

Go to Zircon

Go to Apatite Diamond, garnet, spinell. Zircon Beryl, Apatite -------------------------------------------------- TRIGONAL SYSTEM ORTHOROMBIC SYSTEM MONOCLINIC SYSTEM (Subdivision ofrepparttar 109302 hexagonal system) Go to Topaz

Go to Orthoclase

Go to Corundum Go to Tourmaline Calcite, corundum, tourmaline, quartz. Chrysoberyl, topaz Orthoclase ------------------------------------------------- TRICLINIC SYSTEM The symmetry of crystals : appearrepparttar 109303 following symmetrical operations: > > Rotation

Inversion by symmetry plane

Madagascar Tourmaline

Written by Alain Darbellay GGGems

2004 All rights reserved. (Na, Li,Ca) (Fe2, Mg, Mn, Al)3 Al6 I(OH)4 I (BO3)3ISi6O18I Crystallographic properties: Trigonal. Hardness 7 - 7.5 Density 3.02 to 3.26 Refractive index: 1.62 - 1.64 Chemical Properties: Alumina borosilicate with fluorine. Occurences: Inrepparttar acid magmatic rocks and associated pegmatites, limestones and schists, placers. Coloured tourmalines are related to sodolithic pegmatites. One distinguishes two principal types of tourmalines:repparttar 109293 hexagonal type andrepparttar 109294 triangular one. The hexagonal type is especially characterized byrepparttar 109295 presence, inrepparttar 109296 prismatic zone, of repparttar 109297 well developed S1 faces, and those of L always narrow. Whenrepparttar 109298 crystals Bi-terminated, one finds withrepparttar 109299 one ofrepparttar 109300 ends ofrepparttar 109301 ternary axisrepparttar 109302 rhomboedron R, and withrepparttar 109303 other samerepparttar 109304 rhomboedron combined with that (0111) = P. The triangular type, here is never finished atrepparttar 109305 two ends, it is characterized byrepparttar 109306 prevalence of faces I inrepparttar 109307 prismatic zone, while those S are very narrow just as those S2 which accompany them. The crystals onrepparttar 109308 finished end carryrepparttar 109309 base C, combined with repparttar 109310 rhomboedron R; inrepparttar 109311 same way sometimes withrepparttar 109312 rhomboedron P andrepparttar 109313 base C 1 2 3 4 Fig. 1& 2 : Triangular type Fig. 3 & 4 :Hexagonal type Very rare type of Rubellite from Antsongombato tourmaline: white head and red body. 5 6 Crystal ofrepparttar 109314 hexagonal type finished Polychrome tourmaline being in Tsilaizina, Madagascar. at a peak frequently found in Tsilaisina. Liddicoatite Tourmaline Deep-PinkTourmaline Blue-greenTourmaline. Indigolite from Anjanabonoina. Antsongombato type. ( Kunar valley, Afghanistan.) Colors of tourmalines: Blue is due to bivalent iron, (magnesium gives a clearer blue)repparttar 109315 manganese produce tone

Cont'd on page 2 ==> © 2005
Terms of Use