The blue of a sapphire and the blue of a topaz will vary ... When it comes to the types of stones, there are precious and semi-precious stones. The only four precious stones are the Big 4 ...
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A blue miracle in the Eifel: How sapphires formed in volcanoesResearchers at Heidelberg University are studying the formation of this characteristically blue ... of sapphire. Why this extremely rare variant of corundum is frequently found in this type ...
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