Natural vs Heated vs Treated Gemstones: How to Read an IGI, GIA or IIGJ Certificate

A gemstone can be 100% natural and still not be in its natural state. It may have been heated, filled with glass, dyed or diffused, and the word "natural" on a label will not tell you. For astrological use, where the gemstone's natural condition is the whole point, that difference matters. This guide, from the House of Shubh Gems, India's most trusted name for natural gemstones for over 25 years, explains the terms, the treatments and how to read a laboratory report.

Natural, Heated or Treated: What Is the Difference?

• Natural, unheated, untreated: Formed by nature and only cut and polished. This is the only category we sell at Only Natural Gemstones.
• Natural but heated: A real gemstone, but heated to improve its colour or clarity.
• Natural but treated: A real gemstone altered by diffusion, filling, dyeing, irradiation or coating.
• Synthetic (lab-grown): Made in a laboratory with the same chemistry as the natural gemstone. Simulants merely imitate its look.

Common Gemstone Treatments

• Heating: Uses temperatures of roughly 800°C to 1800°C to improve colour and clarity.
• Heat with pressure: Adds pressure of nearly 1 kbar at high temperature, used on some Sri Lankan sapphires to deepen blue.
• Diffusion: Introduces colour-causing elements into the surface layer.
• Fracture or glass filling: Fills cracks with glass or resin to improve clarity.
• Oiling or resin: Fills fractures, common in emerald.
• Dyeing and coating: Adds artificial colour to the gemstone.
• Irradiation: Uses radiation to change colour.

Heating is by far the most common. Industry estimates suggest around 90 to 95 percent of commercial sapphires are heated, and no one can tell by eye. Only laboratory testing can reveal it.

Why Heated and Treated Gemstones Do Not Work as Effectively

A natural gemstone forms over millions of years, its atoms settling into an ordered crystal lattice. Heating and heat with pressure use very high temperatures, and diffusion and filling add foreign material. These processes can dissolve natural inclusions, alter colour-causing elements and disturb the gemstone's internal structure.

In Vedic tradition, that structure is what allows a gemstone to carry planetary energy. When it is altered artificially, the gemstone is believed to lose its ability to channel cosmic energy effectively. A treated gemstone may look beautiful, but for remedial use, only a 100% natural, unheated, untreated gemstone is the right choice.

How to Read a Gemstone Certificate

A gemstone report is the identity document of one specific gemstone. Read these five lines:

• Report number. Every report carries a unique number. Verify it with the laboratory itself. GIA, for example, offers an online Report Check.
• Identification. This states the species and variety, and whether the gemstone is natural or synthetic. Check that it matches what you bought.
• Treatment or comments. This is the most important line. For sapphire and ruby, "no indications of heating" means the laboratory found no evidence of heat treatment, while "indications of heating" means it did. Other treatments, such as filling or diffusion, are named here too.
• Weight, measurements and photograph. These must match the gemstone in your hand.
• Origin. This appears only when the laboratory can determine it, and it is an expert opinion, not a guarantee.

One honest point: "no indications of heating" means the laboratory's methods found no evidence at the time of testing. It is the strongest statement a laboratory can make, which is why careful sourcing matters as much as the report.

Which Laboratories to Trust

Insist on a report from an independent laboratory, never a seller's own certificate. Every gemstone at Only Natural Gemstones is 100% natural, unheated and untreated, and is certified by IGI, IIGJ and GIA:

• GIA (Gemological Institute of America): Reports record species, variety, weight, measurements and any detected treatment, with security features and a verifiable report number.
• IGI (International Gemological Institute): Colored stone reports identify the species and variety with a photograph, state origin when conclusively determined, and note permanent treatments in the comments.
• IIGJ (Indian Institute of Gems & Jewellery): A GJEPC project supported by the Ministry of Commerce & Industry, with laboratories in Jaipur and Delhi. Its reports identify whether a gemstone is natural, lab-grown or a simulant, and disclose treatments.

Red Flags to Watch For

• No certificate, or one issued by the seller
• A report number that cannot be verified with the laboratory
• A missing or unclear treatment line
• Weight, measurements or photograph that do not match your gemstone
• A price far below the market rate for the stated quality

Frequently Asked Questions

What is the difference between natural and treated gemstones?

A natural gemstone is a real gemstone from the earth. A treated gemstone is a natural gemstone that has been altered, for example by heating, filling, dyeing or diffusion, to improve its look.

What does "no indications of heating" mean?

It means the laboratory found no evidence that the gemstone was heated. It is the standard to look for in an astrological sapphire or ruby.

Can I tell if a gemstone is heated by looking at it?

No. Heat treatment cannot be reliably judged by eye. Only laboratory testing can identify it.

Is a heated gemstone fake?

No, it is a genuine gemstone. It is simply not in its natural state, which is why tradition advises unheated gemstones for astrological use.

How do I verify my gemstone report?

Use the report number to check with the issuing laboratory, and confirm that the weight, measurements and photograph match your gemstone.

Shop Certified Natural Gemstones

Explore our collection of unheated, untreated gemstones, from the House of Shubh Gems, each with an independent laboratory report.

Buy only natural. Buy only certified.

Sourced with Care. Chosen for Purpose. Delivered with Trust.