Quy Chau is a ruby and pink-sapphire mining district in Nghe An Province, north-central Vietnam, situated within the Song Da Rift metamorphic belt. The deposit, first formally reported in the 1980s and widely known in the international trade from the early 1990s, produces marble-hosted rubies geochemically and visually similar to the classic material of Mogok in Burma — vivid red, strong fluorescence, low iron content — and shares the front rank of South-East Asian ruby sources alongside Burma and Mozambique in the contemporary trade.

Geology

The Quy Chau rubies form in marble: a metamorphosed limestone in which corundum crystallises during regional metamorphic events involving fluid mobilisation of aluminium and chromium. Marble-hosted ruby deposits are characteristically low in iron because the marble host itself is iron-poor; the resulting corundum receives chromium for red colour without significant iron quenching of fluorescence. This geochemistry is the technical reason for the visual character of the finest Quy Chau, Mogok, and central-Asian rubies: vivid red colour with strong red fluorescence under ultraviolet light and even under ordinary daylight, producing an apparent inner glow.

The Song Da Rift belt continues across the Vietnamese-Lao border and is part of the broader marble-hosted ruby province that extends through Burma, Yunnan in southern China, Tajikistan, and northern Afghanistan. Quy Chau and the related Vietnamese deposit of Luc Yen are the principal commercial ruby sources within Vietnam.

Inclusions and identification

Quy Chau rubies share with other marble-hosted material a characteristic inclusion suite: calcite crystals (often with characteristic euhedral rhombohedral form), negative crystals, rutile silk in two or three directions producing asterism in cabochon, and feathers. Trace-element chemistry — particularly low iron, elevated chromium, and modest vanadium and gallium — separates Quy Chau material from basalt-hosted rubies such as those from Thailand and parts of Cambodia.

Distinguishing Quy Chau from other marble-hosted sources, particularly Mogok and Mozambique, is more demanding. Major laboratories — GIA, Gübelin, SSEF, Lotus — issue origin opinions on Vietnamese material based on a combination of inclusion features and trace-element fingerprints, but the determination is not always conclusive and laboratory practice is to decline an opinion where the data permit multiple interpretations.

Treatment

The majority of Quy Chau rubies on the market are heat-treated to dissolve rutile silk and improve apparent colour and clarity. Heat alone, without residue, is broadly accepted in the trade with appropriate disclosure. More aggressive treatments — lead-glass filling of fractures, beryllium diffusion — occur in Vietnamese material as elsewhere and require explicit disclosure under AGTA and Confédération Internationale de la Bijouterie standards. Unheated Quy Chau rubies of fine colour and clarity command significant premiums and are documented as such by the major laboratories.

In the trade

Vietnamese ruby production reached the international trade primarily through Bangkok and Hong Kong cutting and dealing centres, with the Luc Yen and Quy Chau fields supplying both centres in roughly comparable volumes. Production volumes are smaller than those of Mozambique, which has dominated the global ruby supply since the Montepuez discoveries of 2009, but fine Quy Chau material remains commercially important and laboratory-confirmed Vietnamese origin contributes to the value of top stones.

Further reading

• GIA — ruby reference
• GIA Gems & Gemology — Vietnamese ruby field reports
• Lotus Gemology — ruby origin and inclusion references
• ICA — ruby and Vietnam