Machine-learning Applications in Gemmology: Classifying the Geographic Origin of Ruby and Sapphire Using Chemical Data. - Seneewong-Na-Ayutthaya, Montira; Sripoonjan, Tasnara; Wanthanachaisaeng, Bhuwadol; Leelawatanasuk, Thanong; Lhuaamporn, Thanapong; Suwanmanee, Waratchanok (Journal of Gemmology, 2025)