Diamond Treatments Explained: HPHT, Irradiation, and Fracture Filling
TL;DR: Diamond treatments — HPHT and irradiation being the two most common — alter a diamond's colour or clarity after it's mined. Treated diamonds must be disclosed on certification and cost significantly less than untreated stones of equivalent appearance. Treatment isn't fraud when disclosed properly; it's a legitimate category, but you need to know which one you're buying.
What Diamond Treatment Means
Treatment refers to any process applied to a natural diamond after mining to alter its appearance — typically improving colour or clarity beyond what the stone naturally has. Treated diamonds are still natural diamonds; the treatment changes their appearance, not their fundamental material.
HPHT Treatment
High Pressure High Temperature treatment (the same process used to grow HPHT lab-grown diamonds is also used, differently, to treat natural stones) can improve a brownish or yellowish natural diamond's colour, sometimes dramatically. The treatment is permanent and stable under normal wear.
Irradiation and Annealing
Irradiation exposes a diamond to radiation to alter its colour, often producing vivid greens, blues, or yellows not naturally occurring at that saturation. Annealing (heat treatment following irradiation) can shift the resulting colour further. These treatments are also generally permanent, though some irradiated stones can theoretically shift colour under extreme heat exposure.
Clarity Treatments
Fracture filling injects a glass-like substance into a visible crack to make it less noticeable, improving apparent clarity. This treatment is less stable than colour treatments — the filling can be damaged by heat (including jewellery repair work) or harsh chemicals, and can discolour over time.
Why Disclosure Matters
A treated diamond must be disclosed as such on its GIA or IGI certificate, and should cost meaningfully less than an untreated stone of equivalent visual grade — the treatment is exactly why the price is lower. Buying an undisclosed treated diamond at untreated prices is the actual fraud risk here, not treatment itself.
Should You Buy a Treated Diamond?
For colour treatments (HPHT, irradiation), a properly disclosed and certified treated diamond can be genuinely good value — a real natural diamond with improved colour at a lower cost than an equivalent untreated stone. Fracture-filled stones are worth more caution given the stability concerns, particularly if the ring will need future repair or resizing work involving heat.
Buying Treated Diamonds at À Vie Diamonds
Any treated stone we source is clearly disclosed and certified as such — get in touch to discuss whether a treated stone suits your budget and brief.
Frequently Asked Questions
Is a treated diamond still a real diamond? Yes — treatment alters appearance, not the fundamental material. A treated diamond is a genuine natural diamond that's been processed to change its colour or clarity.
Do treated diamonds need to be disclosed? Yes — GIA and IGI certificates state clearly if a diamond has been treated, and this should be reflected in a lower price.
Is fracture filling risky? More so than colour treatments — the filling can be damaged by heat or harsh chemicals, which matters if the ring will need future repair work.
Last reviewed: July 2026 · À Vie Diamonds