gems, corundum, treatments.6, ruby, Myanmar.12, Mong Hsu

Mong Hsu rubies from Myanmar typically include a dark core and a blue patch, but most previous research has focused only on the dark core. This work aims to clearly understand the characteristics of both the dark core and blue patch of Mong Hsu rubies. FTIR analysis showed that both the dark core and blue patch regions exhibited absorption peaks of boehmite (1986 cm⁻¹), diaspore (2115 cm⁻¹), and water (3400–3900 cm⁻¹), but the O–H stretching absorption peaks at 3309 cm⁻¹ and 3078 cm⁻¹ were found only in the blue patch region. UV–VIS–NIR analysis of the dark core region revealed stronger absorption of Cr³⁺ at 405 and 554 nm compared to the blue patch region. In the 600–800 nm range, UV absorption features at 659, 675, and 693 nm—assigned to Cr³⁺ in core group samples—were distinct from those of the blue patch. SEM–EDS examinations disclosed a higher density of microcracks and pores in the core regions compared to the blue patch region.