Located north of Hanoi, in Yên Bái Province, the Lục Yên region is recognized as one of the main sources of gemstones in Vietnam. This mountainous area is particularly renowned for the exceptional richness of its soils in rubies, sapphires, and spinels, making it a prime field for gemological studies and deposit analysis. The site is characterized by a large number of mines,often artisanal, scattered across a rural, hilly landscape. Mining activities generally remain small-scale and rely on traditional, simple techniques: manual extraction of gem-bearing gravels from alluvial or secondary deposits, washing with a pan, followed by careful hand sorting.

 

This context offers a unique opportunity to directly observe real extraction conditions, study local methods, and easily access raw samples freshly taken from the deposit. During explorations conducted in the mines of Lục Yên, several samples of rubies, sapphires, and especially spinels were collected directly on site by Valentin Fejoz. Spinels, in particular, stand out for their wide range of colors from delicate pink to intense red, including orange, violet, and even highly sought-after cobalt blue shades.

 

Special attention was given to the study of inclusions within these Vietnamese gemstones. Using a gemological microscope, Valentin Fejoz produced numerous detailed photographs of these inclusions. Some of them, typical of spinels (and sometimes rubies) from Lục Yên, serve as key indicators for determining origin, distinguishing between natural and treated gemstones, and understanding the geological conditions under which these stones formed.

 

The photographs and field observations made in Lục Yên were subsequently carefully documented and described in the chapter dedicated to rubies and spinels in the book Internal Features of Gemstones, a key reference in the study of gemological inclusions.