Fracture Filling

Fracture filling is controversial because it can be reversible and may degrade over time. Emeralds are traditionally oiled with cedarwood oil or synthetic resins; the degree of filling (minor, moderate, significant) is graded and disclosed on lab reports. Rubies from Mozambique and other origins are sometimes filled with lead-crystal glass, which dramatically improves apparent clarity but adds weight and changes refractive index measurably. A flash effect — bluish or orangey reflections from the filled fractures — is a visual indicator of glass filling in rubies. Ultrasonic cleaners can remove fillings from treated stones.