Madagascar corundums ( Sapphire & Ruby discovery )Written by Alain Darbellay GGGems
Continued from page 1
Ruby in amphibolite. The crystals engaged in rocks, rich in mica have rough faces, encrusted of biotite or muscovite, minerals which also exist at state of inclusions, associated with magnetite and pyrite. Because of its hardness, its inalterability and its density, corundum constitutes a standard mineral of alluvia. Ruby Giant Sapphire in a metamorphic dolomitic limestone. Polychrome Sapphire Blue Sapphire ( origin: Blue Sapphire ( origin: Ilakaka 1999 ) ( origin: Iankaroka 1990 ) Andranondambo 1992 ) Found in sandstones of Isalo in This sapphire comes from a granit, The stone comes from alluvium, shape is rounded. its shape is intact. a metamorphized limestone. The origin of stone is a limestone. · The structure of crystals. It is R.J.Haüy who put forth first assumption, confirmed 200 years later, on structure of crystallized material. He lets drop accidentally a calcite crystal which broke into small rhomboedrons. He supposed whereas crystals were consisted of stacking small rhomboedrons elementary (that he called "integral molecule"), he could reconstitute all known shapes of calcite. In a crystal lattice, three atoms or groups of atoms (nodes), which is not on same line, determine a plan called reticular plan. But there is a great number of these plans: it is enough to choose nodes not strictly nearby. As network is infinite, there is even an infinity of possible plans. The dimension of faces does not play of role. In course of growth, a face can develop more quickly than another. The angle that faces make between them remains constant, since it depend on network. This structure of crystalline material explains law of constancy of dihedral angles. Triangular figure on a Scratches on a rare Stacking in macle Triangles on a translucent colorless corundum. colorless corundum. of a ruby. corundum. Triangular figure on a Triangles in step on a blue Remarkable macle of blue corundum. corundum from Maromby. red corundum. Sapphire & Ruby Safari Gem ruby from Ambatovaravarana. The alluvial ruby deposit of Ambatovaravarana in high plateaus, is in left center on picture, under hill. Macle of blue sapphire. Macle of ruby 60 grms. Information ¦ Cutting Styles ¦ Characteristics ¦ Crystalline Systems ¦ Madagascar Sapphire Andranondambo Sapphires ¦ Blue Sapphire Crystal ¦ Ruby Crystal ¦ Sapphire Slice Your guide to GGGems.com All pictures on this site have been shot by gggems.com Alain Darbellay © 1987 - 2004 gggems.com All rights reserved.
http://www.gggems.com/Madagascan_corundum.htm
| | Madagascar AmethystWritten by Alain Darbellay GGGems
Continued from page 1
Certain minerals present sometimes left forms sometimes right forms. The most known example is that of quartz. The distinction between left quartz and right quartz has a certain importance in electronics industry where one uses piezo-electric properties of this mineral. The negative crystals of hexagonal shape can contain liquids like water, gas, as well as rutile needles, tiny hematite discs, goetite, fushsite or mica. Inclusions of H2O and CO2 in an amethyst from Madagascar. Habitus type of flattened Dauphiné. This marvellous Bi-terminated amethyst of 128 grams also contains water drops in its center. Habitus type of rhomboedron. Enlarge The amethyst scepters are also typical in Madagascar. Here, a scepter in blackberry shape. There, stem of scepter developed by crystallizing around it a quantity of small points in hedgehog. Length:40 mm. Double scepter. Enlarge Head of scepter: 132 grams Enlarge Amethyst in castle on its quartz gangue. 986 grams. Enlarge The fact that sometimes only a thin surface layer of violet color be presents in stone or that this color is not homogeneous, makes often a difficult cutting. The art of lapidary is to place color correctly in order to make homogeneous tone of cut stone. The distribution of color in a cut stone is observed simply by immersing it in water contained in a transparent container and colourless. The color of amethyst varies from purple reddish to purple bluish while passing by straightforwardly crimsons tone. Thus of very variable intensity, color is often laid out in stripes parallel to final faces of crystal. Enlarge ¦ Cutting Styles ¦ Characteristics ¦ Crystalline Systems ¦ ¦ Amethyst Crystal 1 ¦ Amethyst Crystal 2 ¦ Amethyst Scepter ¦ Faceted Amethyst ¦ gggems.com © 1987 - 2004 gggems.com All rights reserved.
http://www.gggems.com/madagascar_amethyst.htm
|
