Modern Cultivation of Freshwater Pearls in China: Advances in Materials, Technique

In the accretionary Hellenides Orogen, gems occur in various rock types of mainly four tectonometamo

Gem-quality sapphires containing ‘exotic’ elements such as Sn, Nb, Zr, Ta, W, are of special int

Fancy colour diamonds that derive their colour from nitro- gen-related defects (such as N3/N2 center