Treatments & Enhancements
Over 95% of the sapphires sold commercially have been heat-treated to improve their colour and clarity. Understanding what treatments exist, how they are detected, and how they affect value is not optional knowledge for any serious buyer — it is the foundation of an informed purchase. This hub covers every major treatment applied to coloured gemstones, from the universally accepted to the deeply problematic.
Context
Why treatments matter
The coloured gemstone market operates on a principle that is deceptively simple: a stone's value is determined by its beauty, rarity, and the degree to which that beauty is natural. Two sapphires that look identical to the naked eye can differ in value by a factor of five or more based solely on whether one has been heated and the other has not.
This is not arbitrary. An unheated sapphire that displays fine colour achieved its appearance through millions of years of geological process — the precise balance of trace elements, temperature, and pressure required to produce saturated colour without human intervention. That geological rarity is what the market values, and what a laboratory report confirms.
For buyers, understanding treatment is the single most important factor in making a sound purchase. For investors, it determines whether a stone will hold and grow in value over decades. For jewellers, it is a matter of professional integrity and legal compliance.
95%
of sapphires on the market have been heat-treated to improve appearance
Reference
Understanding treatments
Each treatment has different implications for durability, disclosure, and market value. Here is what every buyer should know about the five most common enhancements encountered in coloured gemstones.
Heat Treatment
Extremely common — over 95% of sapphiresThe most widespread enhancement in the coloured stone trade. Rough sapphire is heated to between 1,200 and 1,800 degrees Celsius, causing trace elements to migrate within the crystal lattice and rutile silk to dissolve. The result is improved colour saturation and clarity. Heat treatment is permanent, stable, and considered an accepted trade practice — but it must be disclosed, and unheated stones command a significant premium.
Value impact: Reduces value by 2 to 5 times compared to an equivalent unheated stone.
Beryllium Diffusion
Moderate — particularly in yellow and orange sapphiresA more aggressive form of heat treatment in which beryllium is introduced into the furnace atmosphere. The beryllium atoms diffuse into the crystal lattice, creating or intensifying yellow, orange, and padparadscha-like colours that were not present in the original rough. Unlike standard heating, beryllium diffusion can create colours that the stone never possessed naturally.
Value impact: Dramatically reduces value. Beryllium-diffused stones are worth a fraction of naturally coloured equivalents.
Lead-Glass Filling
Common in low-grade rubyHeavily fractured, near-opaque ruby is filled with high-refractive-index lead glass to improve transparency and apparent colour. The glass fills fractures and cavities, creating the illusion of a clean, transparent stone. This treatment is not stable — the glass can deteriorate with exposure to acids, heat, and even household chemicals. Lead-glass-filled rubies are not considered genuine gemstones by most reputable dealers.
Value impact: Stones are effectively worthless as natural gems. Must be disclosed as composite material.
Flux Healing
Occasional — primarily in ruby and some sapphiresDuring high-temperature heating, a flux (typically borax) is added to the furnace. The flux dissolves into surface-reaching fractures and, as the stone cools, recrystallises as synthetic corundum within those fractures — effectively "healing" them. The result is a stone with improved clarity, but one that now contains small amounts of synthetic material along its former fracture planes.
Value impact: Significant value reduction. Flux residues are a diagnostic marker that laboratories specifically report.
Oiling & Resin Filling
Standard practice for emeralds; occasional in other stonesOil or resin is introduced into surface-reaching fractures to reduce their visibility and improve apparent clarity. This is the traditional treatment for emerald and is considered an accepted trade practice for that gem species. In sapphires and rubies, oiling is far less common and is generally viewed less favourably. The treatment is not permanent — oil can dry out or be removed by cleaning.
Value impact: Accepted for emeralds when disclosed; viewed negatively in corundum and reduces value accordingly.
We verify the treatment status of every stone in our collection through independent laboratory testing. To learn more about our verification process, see our verification standards.
Guides
Treatment guides
Coming Soon
More treatment guides on the way
How to detect heated sapphires — what laboratories look for
Treatment disclosure requirements — trade standards and legal obligations
Beryllium diffusion explained — the treatment that changed the sapphire market
Heat treatment vs no heat — a visual comparison guide
Serendib Gemstones
Only certified, fully disclosed stones
Every stone in our collection carries a current GIA or GRS report with full treatment disclosure. No surprises, no ambiguity — just verified gemstones from a trusted source.