Chaung-gyi, Mogok Township, Pyin-Oo-Lwin District, Mandalay Region, Myanmar

The general area of Chaung-gyi (Big Stream) is situated about 7 km from Mogok township and it is only accessible by 4-wheel drive vehicle. The long, narrow Chaung-gyi valley runs from south-west to nort-heast. The Chaung-gyi-chaung is the main stream and flows south-west to north-east into the lowlands of Momeik.

The area is composed of igneous rocks (leucogranite, syenite), and metamorphic rocks (marble, calc-silicate, gneiss). The calc-silicate rocks are tightly folded and minor drag foldings are observed. The metamorphic rocks are often faulted and intruded by leucogranite and syenite. The Lisu, Shan, Nepali/Gurkha and Palaung ethnic minorities live in the Chaung-gyi valley in separate villages, and work in the numerous MGE-joint venture mines situated nearby. In 1999 there were about 50 legal joint ventures in and around Chaung-gyi, employing more than 1.000 miners working on the valley floor in one daylight shift. Some illicit mining takes place on the adjacent hillsides.

Gem mining is carried out through myaw-dwin, lebin-dwin and open-pit methods. The gems are found in the secondary deposits (mostly alluvium at the valley floor), as well as at the adjacent primary deposits (marbles, skarns and pegmatites). The stream supplies the water required for washing the gems found in the valley. Many gems and minerals including pitchblende, a radioactive mineral, are found at Chaung-gyi.

Ref: Ted Themelis (2008) Gems and Mines of Mogok, p. 184

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