Mai Sutaung is a ruby-mining locality within the Mogok Stone Tract in northern Myanmar, the corundum belt that has produced the bulk of the world's finest Burmese rubies for several centuries. The locality is one of a number of named villages and workings within the broader Mogok district, and corundum from Mai Sutaung shares the marble-hosted geological setting and the low-iron, chromium-coloured chemistry that define the region's gem ruby. As with the other Mogok workings, the laboratory and trade origin call for stones from Mai Sutaung is conventionally Mogok rather than the specific sub-locality.

Geological setting

Mai Sutaung sits within the Mogok Metamorphic Belt, the high-grade metamorphic terrain that hosts the principal Burmese ruby deposits. The host rock is a coarse-grained, white to pale-grey metamorphic marble, in which corundum crystals grew under conditions of relatively low silica activity and limited iron availability during the Paleocene to Eocene-age metamorphism associated with the Indo-Asian plate collision.

The chemistry of the Mai Sutaung corundum, as with other Mogok workings, is characterised by very low iron content and significant chromium content contributed from associated mafic intrusions. The combination produces the strong red fluorescence under daylight and ultraviolet excitation that is the hallmark of fine Burmese ruby and the principal optical distinction from the iron-rich rubies of Mong Hsu, Mozambique, and Madagascar.

Recovery and working history

As with other Mogok workings, ruby is recovered at Mai Sutaung from primary marble outcrops, from weathered residual deposits at the surface, and from alluvial gravels in the streams and rivers that drain the marble belt. The artisanal and small-scale sector accounts for most of the production, with periodic engagement from larger operators in the primary marble mining.

The locality has been worked for centuries alongside the other Mogok villages, with documentary references in Burmese, Chinese, and European sources extending back into the colonial period. The British colonial Burma Ruby Mines Limited consolidated the principal Mogok workings under industrial management in the late nineteenth century, and Mai Sutaung was within the area of operation. Subsequent twentieth- and twenty-first-century operation has been under various Burmese state and private arrangements.

Ruby characteristics

Mai Sutaung rubies share the characteristic gemmological profile of Mogok material in general. Body colour is a pure red — at the upper end approaching the pigeon-blood standard — with strong fluorescence under both daylight and ultraviolet excitation. Iron content is low, supporting the strong fluorescence and distinguishing Mogok material from the iron-rich corundum sources. Inclusions characteristic of the source — silk-like rutile needles, calcite crystals, and growth zoning visible under microscopy — provide the basis for laboratory origin determination.

Production from Mai Sutaung, as with most of the Mogok workings, is dominated by smaller stones. Larger fine pieces are exceptional and command very substantial premiums, particularly when accompanied by Mogok origin certification from one of the principal coloured-stone laboratories.

Origin determination

For laboratory purposes, the relevant origin call for corundum from Mai Sutaung is Mogok, Myanmar or Burma, depending on the laboratory's preferred terminology. The principal coloured-stone laboratories — Gübelin, SSEF, AGL, Lotus Gemology, and GIA — issue origin opinions for fine rubies of plausible Mogok origin where the analytical data support a confident attribution. The combination of low iron, high chromium, characteristic trace-element profile, and characteristic inclusion suite is typically sufficient for confident Mogok attribution at the upper end of the market.

Sub-locality attribution within the Mogok district is generally not made at the laboratory level. The geological and gemmological signatures of Mai Sutaung and the other Mogok workings are too similar to support reliable sub-locality discrimination on currently available analytical data, and the trade and laboratory practice converges on the umbrella Mogok origin call.

In the trade

Stones marketed as Mai Sutaung rubies in dealer parlance are within the broader Mogok category and trade at the prevailing premium that documented Mogok origin commands over Mozambique and other commercial sources. The premium for Mogok ruby of fine quality remains substantial — typically a multiple of two to four times comparable Mozambique material at the upper end of the market — and is the principal commercial reason for commissioning origin certification at the major laboratories.

Further reading

• Lotus Gemology — Mogok ruby and sapphire
• GIA Gems & Gemology — Mogok corundum articles
• Gübelin Gem Lab — origin determination