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The Origin and Recovery of Gemstones
Ruby and Sapphire
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absorption spectrum amber America appearance bands base beads blue brown called carbonate carried carved cause chemical colour colourless common composition consists containing corundum County crystals cultured dark density deposits diamond directions district double edge effect emerald faces facets Figure fluorescence garnet gemstones give glass glow green hardness heat imitation important inclusions Indian indices iron Italy ivory jewellery known layer light lines localities marble material method mineral mines Mohs's scale mountains natural North obtained occurs opal ornamental owing oxide oyster particularly pearls pieces pink placed polished probably produced quartz range rarely refractive index reported river rock ruby sapphire seen shell shown silicate similar sometimes South specimens spinel stones strong structure surface synthetic termed topaz tourmaline true turquoise ultra-violet light United usually varies variety x-rays yellow zircon