Heated vs Unheated Blue Sapphire: What Is the Difference?
When shopping for a blue sapphire ring you will often see the terms heated and unheated. Both are natural sapphires. The difference is whether the stone has been heated to improve its colour and clarity. That difference has a large effect on price, so it is worth understanding before you buy.
What is a heated sapphire?
Heating is the most common treatment for sapphire. The stone is heated to a high temperature to deepen the blue and dissolve fine inclusions that make it look cloudy. The result is stable and permanent and does not fade with wear. Most sapphires in the jewelry market have been through this process, and it is widely accepted as long as it is disclosed.
What is an unheated sapphire?
An unheated sapphire already had good colour when it was mined, with no heating. Such stones are far rarer, so they can cost several times more than a heated sapphire of similar appearance. A laboratory report will usually state that there are no indications of heating.
A quick comparison
- Authenticity: both are natural sapphire.
- Appearance: they can be equally beautiful. The untrained eye cannot tell them apart.
- Rarity: unheated is far rarer.
- Price: unheated costs more for the same colour and size.
- Durability: the same. Sapphire is 9 on the Mohs scale whether heated or not.
Treatments that are not ordinary heating
Ordinary heating is not the same as diffusion or filling. In diffusion, colouring elements are driven into the outer layer of the stone, so the colour does not come from the stone itself. Some sapphires also have filled fractures. Stones treated this way are worth far less and must be clearly disclosed by the seller.
How can you tell?
Heated or unheated cannot be confirmed with the naked eye. A gemological laboratory can determine it by examining the inclusions inside the stone under a microscope and with analytical instruments. For a higher-value sapphire, especially one sold as unheated, ask for a laboratory report.
Which should you choose?
- Choose heated if your priority is beautiful colour and a larger size for the same budget.
- Choose unheated if you value rarity and are willing to pay more, with a laboratory report as proof.
- Either way, put an even, lively blue first, then cut and clarity.
Talk to Kimfook Jewelry
Kimfook Jewelry sells natural diamonds and natural gemstones only, set in SNI-audited 18K gold. Browse our natural blue sapphire rings, visit the showroom at Ruko Spectra Blok 23B No. 12, Alam Sutera, South Tangerang, or message us on WhatsApp +62 811-270-055. Not in Jakarta? See how to buy online with insured delivery to Bali and across Indonesia.
Frequently asked questions
Is a heated sapphire real?
Yes. A heated sapphire is a natural sapphire that has been heated to improve colour and clarity. The result is permanent and the practice is accepted in the market.
Why is unheated sapphire more expensive?
Because it is far rarer. Only a small share of sapphires have good colour without heating.
Can you tell heated from unheated sapphire by eye?
No. Only a gemological laboratory can confirm it, by examining the inclusions inside the stone.
