Why It Matters to You
Value
Treated gemstones can be significantly less valuable than untreated stones of similar appearance. Knowing a gem’s treatment history helps you understand if you're paying a fair price.
Stability and Care
Some treatments make gems more stable; others do the opposite. For instance, a heat-treated sapphire is stable and permanent, while a dyed turquoise may lose its colour over time or react poorly to cleaning.
Disclosure
Ethical retailers are required to disclose any treatments a gemstone has undergone. This transparency helps build trust and ensures buyers aren’t misled by artificially enhanced beauty.
Durability
Filling can improve a gemstone’s durability, making it less likely to chip or crack. However, coated gems may become scratched or lose their lustre more quickly.
READ ON
When you admire the brilliance of a ruby or the glow of an emerald, it’s easy to forget that many gemstones don’t arrive in jewellery stores in perfect condition. In fact, most have undergone treatments—processes used to enhance their appearance, clarity, colour, or durability. While these enhancements can make gems more attractive, they also affect value, care requirements, and purchasing decisions.
Common Gemstone Treatments
1. Heating
One of the oldest and most widespread treatments, heating is used to improve the colour and clarity of gems like sapphires, rubies, and amethysts. This process mimics natural heat conditions deep in the earth, transforming dull stones into vibrant gems.
2. Dyeing
Dyeing enhances or changes the colour of a gemstone by soaking it in a coloured solution. Pearls, jade, and coral are often dyed to produce more vivid hues. However, dyed colours may fade over time and should always be disclosed at the time of sale.
Left: A close-up of the natural green area shows a smooth, diffused colour texture.
Right: A close-up of a dyed area shows colour concentrations in the thin gaps between the crystal grains of jadeite.
Photomicrograph by Jonathan Muyal
3. Coating
Some gemstones are coated with a thin layer of material to enhance colour or surface lustre. This is more common with lower-cost gems or fashion jewellery, and the coatings may wear off with time.
4. Fracture Filling
Fracture filling involves injecting a gem with glass, resin, or other materials to fill internal cracks or inclusions. This is frequently seen in rubies and diamonds, where the treatment improves visual clarity.
Oiling
Primarily used on emeralds, oiling involves filling surface-reaching fractures with oils to improve clarity. Since oil can dry out or be removed during cleaning, this treatment often requires maintenance.
Final Thoughts
Understanding gemstone treatments empowers buyers to make informed, confident decisions. Whether you're investing in fine jewellery or shopping for a statement piece, don’t hesitate to ask about treatment history and care guidelines, or ask a registered NCJV Jewellery ValuerTM for quality assessment report before your purchase.