Page 46 - 18 KARATI GOLD&FASHION 219
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             Glimmers of Sapphire
                               Characteristics
Sapphires belong to the variety of corundum, aluminium oxide crystals. The name corundum derives from the Sanskrit term “kuruvinda”, while the name sapphire derives from the Latin “sapphirus” (Greek “sappheiros”) which means light blue. Some make it derive from the Hebrew “sappir” (precious stone) or from the Sanskrit “sanipriya”. Corundum, in its infinite range of colours, includes both sapphires and rubies, the latter differentiated by the red colour. Usually those who think of sapphire imagine it to be blue, but there are colourless sapphires, pink, orange, green sapphires. The shades of the gem range from sky blue to light blue, to gentian blue. The most valuable sapphires have a cornflower blue colour, without reaching shades that are too dark, while each reflection of black, grey or green reduces the value of the gem. The sapphire distinguishes itself from the other varieties of corundum for the content of colouring oxide; in particular, blue sapphire owes its shade to a high percentage of pure aluminium, more than 90%, together with iron oxide, titanium oxide and cobalt oxide. Sapphire has a hardness of 9 on the Mohs Scale, equal to that of the ruby, but it doesn’t have a splitting plane and it cannot be sectioned with a single cut like the diamond. It changes colour if the stone is rotated under a source of transmitted light, a phenomenon called pleochroism, which should be considered in the cutting phase. It can also show asterism, the production of a reflection of star light, which can be highlighted only if the cabochon cut is correctly oriented.
In alto da sinistra: anello in zaffiro taglio cabochon, diamanti taglio circolare, platino, anno 1970; anello con zaffiri degradé, diamanti taglio circolare, oro bianco 18 Kt, anno 1990; anello con zaffiro esagonale taglio a gradino, diamanti esagonali, oro bianco 18 Kt. A fianco: anello con zaffiro cabochon a pan di zucchero, zaffiri blu, rosa e viola a taglio circolare, argento e oro. Firmato JAR.
Top, from left: ring in cabochon cut sapphire, circular cut diamonds, platinum, 1970; ring with dégradé sapphires, circular cut diamonds, 18 Kt white gold, 1990; ring with hexagonal step cut sapphire, hexagonal diamonds, 18 Kt white gold. At the side: ring with sugarloaf cabochon sapphire, blue, pink and violet circular cut sapphires, silver and gold. By JAR.
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