Gems & Gemology, Fall 2011, Volume 47, No. 1
Ruby and Sapphire from the Tan Huong-Truc Lau Area, Yen Bai Province, Northen Vietnam
Nguyen Ngoc Khoi, Chakkaphan Sutthirat, Duong Anh Tuan, Nguyen Van Nam, Nguyen Thi Minh Thuyet, and Nguy Tuyet Nhung
Primary and secondary deposits in the Tan Huong–Truc Lau area of northern Vietnam’s Yen Bai Province have supplied rubies (especially star rubies) and some sapphires—mostly of cabochon quality—for more than a decade. The gems are typically translucent to semitransparent and pink to purplish or brownish red, with rare color zoning. The most distinctive features of this corundum after polishing include growth zoning and asterism. The samples contain relatively high amounts of Fe and variable Ti and Cr. The geologic origin and gemological properties of this corundum are distinct from that of the adjacent Khoan Thong–An Phu area.