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4 articles
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Corundum
Sapphire: The Many Colors of Corundum
A complete guide to natural sapphire: the chemistry behind its many colors, the world's major deposits, treatments and synthetics, and the famous stones and record crystals behind its reputation.
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Hardness
Gemstone Hardness and the Mohs Scale Explained
What hardness in a gemstone actually means, how the Mohs scale came about, why its steps are so uneven, and whether anything is genuinely harder than diamond.
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Hardness
Gemstone Hardness List
Mohs hardness values for more than 140 gemstones and gem materials, from talc at 1 to diamond at 10, with the mineral species behind each trade name.
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Corundum
Kashmir Sapphires: The Legend of the Blue Treasure
Why Kashmir sapphires outprice every other blue: the legendary Paddar mines, the science behind the velvety cornflower blue, and the records they set at auction.
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