:: SUWA/Dictionary-Untreated Gemstones::

Weight : 5.46ct
Size(mm) : L9.9 x W8.5 x D6.97
Mogok, Untreated
Gem Quality

Rubies that are beautiful in their original crystal form are rare. Rubies from the historical Mogok district, and from the Mong Hsu mines, that began production in the late 1980s; are representative of the material from Myanmar. Not all of these rubies are heated. Gems that are inherently beautiful, with few defects, do not require treatment.

The ruby shown on the left is an untreated ruby from Mogok. It is a superb piece with high transparency and brilliance. A dark color and a well-balanced mosaic pattern, combined with a large size, result in beautiful "pigeon-blood" rubies. The untreated rubies that SUWA uses have few imperfections and are "naturally" beautiful gemstones.

Map of Major Sources

Untreated Mogok Ruby

Untreated and heated ruby

When comparing Mogok rubies on the quality scales for untreated and heat treated rubies, there is a noticeable difference in transparency resulting in a difference in color and beauty. Untreated material is a refreshing transparent red, while the treated material has a somewhat lower transparency and diminished clearness. This is due to the changes in the material's internal characteristics and surface, the effect of high temperatures on the ruby crystal. It is difficult to look at an individual stone and determine if it is heat-treated or not, but when making comparisons over the whole quality scale, the difference can be noted. Some ruby dealers in the cutting locales claim to be able to make this distinction when comparing several rubies together.

Silk inclusions
Silk inclusions in this untreated Mogok ruby cross at 60 degrees.
Occasionally, "stubby" crystal inclusions can also be found.

Characteristics of Heated Ruby
Some heated corundum has snow ball inclusions, like in the example on the left. These are crystals inside the stone that have melted and become round during heat treatment.

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