Green stone 10k yellow gold vintage ring sz 6

Vintage BDA Budlong Docherty & Armstrong 10K Ring Sz 6 Shows light wear from use, including surface scratches, and light dents on the shank. Was sold to me as an Emerald but I doubt it is. My guess would be either a green garnet, tourmaline or synthetic stone although I see no bubbles in it. The seller said the stone tested as an emerald. I’m not a gemologist so it’s sold as is! The stone is in good condition but is also slightly loose. It won’t fall out, but can be repaired for around $15.