Figure 1. This cross section through ancient thickened continental lithosphere and underlying mantle shows the two major depth intervals of diamond formation. The majority of mined diamonds originate ...

Recently, the author analyzed an interesting 41.51 ct faceted bicolor beryl (figure 1) composed of aquamarine and opaque white beryl. This gem belongs to Brazilian gem dealer Veber Leite and is part ...

In November 2022, a parcel of 24 approximately 0.5–1.2 ct spinel crystals, described as cobalt-diffused, were obtained directly from a treater by the research team at GIA in Bangkok. Of these, seven ...

Le Ngoc Nang, Pham Minh Tien, Pham Minh, and Pham Trung Hieu Anorthoclase, (Na,K)AlSi 3 O 8, is an uncommon variety of alkali feldspar that is the potassium-rich variety of high albite, distinguished ...

Figure 1. Earthquake depth distribution and overview of plate boundaries. A: Depth distribution of earthquakes worldwide (note the logarithmic scale). Most “regular” earthquakes occur at depths ...

GIAについて 1931年設立の独立非営利組織であるGIA（Gemological Institute of America）は、宝石学における世界有数の権威として認められています。GIAはカラー、クラリティ、カット、カラット ウェイトからなる有名な4Cを考案し、さらに1953年にはダイヤモンドの品質の基準として世界中で認知されて ...

Figure 1. Lath-like mineral inclusions of grandidierite were seen in this sapphire at GIA’s Carlsbad laboratory. Photomicrograph by Nathan Renfro; field of view 2.61 mm. Recently the authors ...

Laboratory-grown CVD rough diamond (left), laboratory-grown HPHT rough diamond (middle) and natural rough diamond (right) Two specimens of faceted crystalized carbon - both are crystal clear and give ...

How Do Lithospheric Diamonds Form? Lithospheric diamonds (box B) often contain detectable nitrogen, implying that they crystallize from carbon- and nitrogen-bearing (C-N-bearing) fluids. Through the ...

GIA has studied lab-grown or manmade diamonds extensively over the past 30 years, and we know a great deal about the methods used to produce them and how they can be recognized. While synthetic ...

Figure 1. A comparison of the Mohs hardness scale and the Knoop hardness scale, a micro-hardness test where a pyramidal diamond point is pressed into the polished surface of the sample with a known ...

The research collection houses about 375,000 mineral specimens from around the world. It’s one of the largest collections of its kind, with great value to the scientific community. The purpose of the ...