A chemical and spectroscopic comparison of two purple gem spinel samples, one of them the first reported example of a spinel with a saturated purple color caused predominantly by chromium and cobalt.

Reports on a visit to a shell nucleus manufacturer and two pearl farms in northern Vietnam, which is emerging as a notable producer.

Shows how the color of Madagascar sapphire is lightened with heating to relatively low temperatures below 1350°C.

Figure 1. This 0.11 ct round brilliant grandidierite is from a new deposit near the town of Tranomaro, in southern Madagascar. Photo by Delphine Bruyère. ABSTRACT A new deposit of grandidierite, ...

Gems & Gemology is the quarterly scientific journal of the Gemological Institute of America.

To do sizing work, bench jewelers use a steel ring mandrel made of tapered, milled steel; and marked in quarter, half, and whole sizes (0.2 mm, 0.4 mm and 0.8 mm, inside diameter respectively). All ...

Useful contact information if you’re looking for a professional to value your gem or jewelry item. GIA does not provide an appraised value for gemstones or jewelry. This service should be performed by ...

カラーストーン鑑別及び原産地レポート 地理的起源の識別レポート。ポリッシュ、ルース、またはセットされた天然ルビー、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のみが入手可能です。 View Sample Report ...

Investigates the presence of fluorescence, rather than iridescence, as the cause of color in blue amber from the Dominican Republic and Indonesia.

GIA Knowledge Sessions, a series of talks and seminars that promise to engage participants in the most diverse and pressing issues in gemology today, including gemstone origin, laboratory-grown stones ...

Figure 1. Pinctada maxima shells hosting blisters or blister pearls. Photo by Nuttapol Kitdee. Introduction The majority of saltwater and freshwater pearls bought and sold in the global jewelry ...

Heating is an accepted treatment for sapphire. But for fine-quality sapphire, confirmation from an independent laboratory like GIA that there is no evidence of heat adds to a sapphire’s rarity and ...