Its main city, Yen The, is also known as Luc Yen, the name given to the ruby and spinel mining district described in the gemological literature (e.g., Kane et al., 1991; Pham et al., 2004a). The aim ...

It features mining pits (the oldest of which dates from 1850) and lift infrastructure, slag heaps (some of which cover 90 ha and exceed 140 m in height), coal transport infrastructure, railway ...