Bi-color sapphire is an exceptional variety of corundum displaying two distinct color zones within a single stone, creating a fascinating visual effect. These unique stones are highly prized by collectors.
9硬度（满分 10）
Heat TreatmentHeat treatment is common and aims to improve color intensity and saturation. It can also slightly modify the distribution of color zones. This treatment is permanent and generally accepted in the market.
Untreated (Natural)Untreated bi-color sapphires are rarer and highly sought after by collectors. They must be accompanied by a laboratory certificate attesting to the absence of treatment. Natural stones retain their original color distribution.
Surface DiffusionLess common treatment that can modify surface colors. Must be disclosed as it significantly affects value. Rarely used on bi-colors as it can mask the natural effect.
