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Diamonds are among nature’s most precious and beautiful creations.

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Colorless diamonds are scarce—most diamonds have tints of yellow or brown.

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Factors used to describe diamonds: Clarity, Color, Cut, Carat Weight

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The rarity of one or more of the 4Cs can affect value.

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The crystal shape of a gem diamond is often the octahedron.

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Trigons—little triangular depressions—occur only on octahedral faces.

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Growth marks

Diamond’s growth marks help experts separate diamonds from simulants.

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Figure 1. Mantle eclogite xenolith (2.8 cm in longest dimension) consisting of clinopyroxene (green) and garnet (red-orange), with a partially exposed octahedral diamond. Photo by Annie Haynes. Gift of Mark Mauthner, GIA Museum no. 37511.
Diamondiferous Mantle Eclogite: Diamond Surface Features Reveal a Multistage Geologic History

Reports on the analysis of a mantle eclogite xenolith with a partially exposed octahedral diamond.

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Figure 1. The 4.04 ct ring fashioned from a single-crystal CVD-grown diamond. Photo by Towfiq Ahmed.
Solid Laboratory-Grown Single-Crystal Diamond Ring

The quality and size of this 4.04 ct CVD-grown diamond ring demonstrate the advancing technology in laboratory-grown diamonds.

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This round brilliant diamond displays twinning wisps that resemble a whale. Photomicrograph by Nathan Renfro; field of view 2.62 mm.
Natural Diamond with Twinning Wisps Resembling a Whale

Examination of a round brilliant diamond reveals twinning wisps in the formation of a whale.

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Figure 2. Left: The deep-UV (<230 nm) fluorescence image showed blue coloration (due to the presence of dislocation bundles) that appeared nominally similar to DiamondView images of natural type IIa diamonds. Right: When the fluorescence was filtered by an orange long-pass filter that blocked wavelengths below 550 nm, the NV-related fluorescence and the striations indicative of CVD growth became apparent. Image by Sally Eaton-Magaña (right).
CVD-Grown Diamond with Few Diagnostic Features

A CVD-grown diamond submitted to GIA requires very careful examination to determine its origin.

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This iridescent ferropericlase crystal with a stress halo measuring approximately 0.7 mm was trapped inside a light brown diamond. Photomicrograph by Kyaw Soe Moe; field of view 1.58 mm.
Iridescent Inclusion in Brown Diamond

An iridescent crystal with a stress halo is observed in a light brown diamond.

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Figure 1. The etch channel in this CVD laboratory-grown diamond extends across the table facet into the crown. Photomicrograph by Elina Myagkaya; field of view 7.19 mm.
CVD “Etch” Channel

The first report of an etch channel–like structure in a CVD laboratory-grown diamond submitted to GIA.

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This etch channel seen in the crown facets of a 1.00 ct diamond with SI<sub>1</sub> clarity (left) resembled a <em>gada</em> (right), a mace-like weapon wielded by the Hindu god Hanuman. Photomicrograph (left) by Deepak Raj; field of view 0.80 mm. Photo (right) courtesy of the Metropolitan Museum of Art.
Inclusion Resembling a Gada in Diamond

An etch channel in the crown facets of a diamond resembles a mace-like weapon.

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Figure 1. This 3.58 ct natural type IIa diamond with H color and SI<sub>2</sub> clarity displayed a unique fluorescence pattern when exposed to deep-UV light. Photo by Diego Sanchez.
Natural Type IIa Diamond with Unusual Red Fluorescence Distribution

A natural type IIa diamond displays a unique fluorescence pattern when exposed to deep-UV light.

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These deep-UV (<225 nm) phosphorescence images of the table (left) and pavilion (right) in a 0.90 ct D-color natural diamond with very low boron showed localized areas of the 500 nm (greenish blue) and 660 nm (red) bands. Images by Evelina Goldort.
Natural Diamond with Unusual Phosphorescence

A rare observation of spatially distinct red and greenish blue phosphorescence in a natural diamond.

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A well-formed colorless breyite crystal reminiscent of a stone making a splash in water. Photomicrograph by Aprisara Semapongpan; field of view 1.07 mm.
Breyite in Diamond

A colorless transparent crystal inclusion in diamond is reminiscent of a stone splashing in water.

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