[Jewelry making - Article 00163] - Re: [Orchid] Gemstones that don't crack easily?

[alex yu]

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    Corundum (sapphire and ruby) can withstand high temperature up to
    1700 to 2000 celsius so normally there will be no problem in heating
    them. We heat thousands carats sapphires in crucibles in the stove to
    improve color. But the critical point is to heat step by step and
    cool down little by little. Sudden change in temperatures can lead to
    crack especially when there are already invisible cracks inside. 

    Sapphires from different origins have different cleavage properties.
    For our sapphires, there is no evident cleavage so the sapphires
    don't crack or chip easily. But sapphire and ruby are also crisp
    material, they can be chipped when falling onto the hard ground. In
    most cases, the thin girdle part will get chipped. 

Alex Yu
Neptune Gem

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