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Ruby is the most valuable variety of the corundum mineral species, which also includes sapphire.

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Fine Mogok Ruby

This fine 2.58-ct. ruby is from Myanmar’s classic Mogok deposit.

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Ruby’s extraordinary red color is caused by traces of chromium.

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Mixed Cut

Like many fine rubies, this example is fashioned as a mixed cut.

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Calcite Matrix

These exceptional ruby crystals on calcite are from Mogok, Myanmar.

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Origin In Marble

The snow white calcite matrix hints at the ruby crystal’s origin in marble.

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Ruby Crystal

The characteristic form of this ruby crystal allows it to be recognized.

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Figure 1. Colorless crystals with high relief in a ruby mined near Caraia in the Montepuez region. Photomicrograph by Wim Vertriest; field of view 3.6 mm.
Update on Inclusion Scenes in Mozambican Rubies

GIA researchers identify zircon inclusions in several Mozambican ruby samples, potentially impacting origin determination criteria used for sources of East Africa ruby.

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Figure 1. Ten corundum samples from the Lofa River in Weasua, Liberia. Photo by Shunsuke Nagai.
Update on Liberian Ruby

Ten Liberian corundum samples are examined in GIA’s Tokyo laboratory.

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Rose channels in a 0.5 ct ruby. Photomicrograph by Aamir Sayed; field of view 0.75 mm.
Rose Channels in Ruby

Examination of a pear-shaped ruby reveals hollow Rose channels.

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Figure 1. An 8.57 ct heart-shaped fracture-filled ruby treated with a zinc glass filling. Photo by Adriana Robinson.
Translucent Ruby Filled with Zinc Glass

Examination of a heart-shaped ruby reveals a zinc glass filler.

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Figure 1. An unusual ruby with coloring reminiscent of a nebula found in the depths of outer space. Photo by Adriana Robinson.
“Nebula” Inclusion in Ruby Beryllium-Diffused to Heal Fractures

Fingerprints resulting from a flux-assisted heating process give a purple-red ruby a unique appearance.

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Figure 1. Greenland’s rubies are characterized by abundant twinning planes. The twinning planes are not altered by the treatment at a larger scale, but features associated with the twinning can be significantly affected by heating. Photo by S. Wongchacree; field of view 14.40 mm.
Characteristics of Treated Rubies from Greenland

An overview of the treatment process of ruby and pink sapphire from Greenland and its effect on inclusion scenes and chemistry.

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Figure 1. Numerous natural-looking dark red solid inclusions were observed in a flame-fusion laboratory-grown ruby. Photomicrograph by Ezgi Kiyak; field of view 2.9 mm.
Unusual Solid Inclusions in Flame-Fusion Ruby

Numerous natural-looking dark red solid inclusions are observed in a flame-fusion laboratory-grown ruby.

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A large cavity partially filled with synthetic overgrowth on the pavilion of a heated Burmese ruby in darkfield lighting (left) and reflected lighting (right). Photomicrographs by Nicole Ahline; field of view 7.19 mm.
Ruby with Interesting Synthetic Overgrowth

Microscopic examination of a ruby at the Carlsbad laboratory reveals synthetic overgrowth indicative of high-temperature heat treatment.

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Figure 1. A handful of gem gravel collected from the Lofa River in Weasua, Liberia, showing the high concentration of ruby material. Photo courtesy of Diamonds for Peace.
Liberian Ruby

A trip to a rural Liberian diamond mining community results in a newly discovered source of corundum.

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