If a buyer requests additional gem testing prior to a sale, the seller may provide this, but at additional cost to the buyer. TREATMENT Codes & Method Table code A: Indicates that this gemstone has no known enhancement, or, this type of gem is very rarely enhanced. code E: ...
The stones used in this study for training and testing are high-quality metamorphic blue sapphires tested by the Gübelin Gem Lab between 2013 and 2020. Metamorphic sapphire is formed in alumina-rich rocks under amphibolite and granulite facies conditions, at temperatures between 500° and 800 °C4...