Amethyst may develop into the more common citrine and rarer green quartz naturally under certain geologic conditions. On the California-Nevada border, just north of Reno, amethyst, citrine, and green ...

Each year basalt-topped Peridot Mesa, on the San Carlos Apache Reservation, is a major source for thousands of carats of gem-quality peridot in sizes suitable for use in modern jewelry. Marketed ...

Most Russian hydrothermal synthetic rubies and pink, orange, green, blue, and violet sapphires—colored by chromium and/or nickel—reveal diagnostic zigzag or mosaic-like growth structures associated ...

ルビー、サファイア、エメラルド、パライバ トルマリン、レッド スピネル、アレキサンドライトが、GIAカラー ストーン鑑別及び原産地レポートの対象となります。しかしながら、これはGIAがすべての場合について原産地をレポートに記載できるという意味 ...