When you purchase a lab grown ruby or sapphire ring, you’re investing in a piece of jewelry that combines beauty, sustainability, and affordability. However, some customers may try to use a diamond tester (also known as a thermal conductivity probe) to verify their gemstone, only to find that it doesn’t “pass” the test. This can lead to confusion and concern.
In this article, we’ll explain why diamond testers aren’t suitable for non-diamond gemstones like rubies and sapphires, how these tools actually work, and what methods you should use to confirm the authenticity and quality of your lab grown gemstone jewelry.
What Is a Diamond Tester, and How Does It Work?
A diamond tester is a handheld device designed to distinguish diamonds from their imitations (like cubic zirconia or glass). It works by measuring a gemstone’s thermal conductivity—the rate at which heat passes through the material. Here’s how it works:
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The tester’s probe is placed against the gemstone.
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A small amount of heat is applied to the stone.
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The device measures how quickly the heat dissipates.
Diamonds have an exceptionally high thermal conductivity, so if the stone dissipates heat quickly, the tester will indicate that it’s a diamond. If not, it will show a negative result.
Why Diamond Testers Don’t Work for Ruby and Sapphire
While diamond testers are effective for their intended purpose, they’re not designed to test other gemstones like rubies and sapphires. Here’s why:
1. Different Chemical Composition
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Diamonds are made of pure carbon (C), which has a unique crystal structure and extremely high thermal conductivity.
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Rubies and sapphires are forms of corundum (Al₂O₃), a mineral with a much lower thermal conductivity.
2. Thermal Conductivity Differences
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Diamonds have a thermal conductivity of 1000–2600 W/m·K, making them one of the best heat conductors in nature.
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Corundum (rubies and sapphires) has a thermal conductivity of only 25–35 W/m·K, far below that of diamonds.
Because of this significant difference, a diamond tester will always show a negative result for rubies and sapphires—whether they’re natural or lab-grown. This doesn’t mean the gemstone is fake; it simply means the tool isn’t designed to test it.
The Limitations of Diamond Testers
1. Narrow Scope
Diamond testers are only effective for distinguishing diamonds from non-diamond materials. They cannot identify other gemstones or determine whether a stone is natural or lab-grown.
2. Potential for Misinterpretation
Some customers mistakenly believe that a negative result means their gemstone is fake. In reality, it just means the stone isn’t a diamond.
3. No Information on Origin
Diamond testers cannot differentiate between natural and lab-grown gemstones. For rubies and sapphires, this distinction requires more advanced testing methods.
How to Properly Test Your Lab-grown Ruby or Sapphire
If you want to verify the authenticity and quality of your lab ruby or sapphire, here are the most reliable methods:
1. Microscopic Examination
Under magnification, natural rubies and sapphires often contain unique inclusions (like mineral crystals or growth patterns). Lab-grown stones may have fewer inclusions or show specific growth features, such as curved striations.
2. Spectroscopic Analysis
Advanced tools like Raman spectrometers or infrared spectrometers can analyze the gemstone’s chemical composition and crystal structure. These methods are highly accurate and can distinguish between natural and lab-grown stones.
3. Fluorescence Testing
Some gemstones exhibit unique fluorescence under ultraviolet (UV) light. For example, natural rubies often show strong red fluorescence, while lab-grown stones may display different patterns.
Why Trust ROISGEMS for Your Gemstone Needs
At ROISGEMS, we take pride in offering only the finest lab-grown gemstone jewelry, backed by transparency, craftsmanship, and cutting-edge technology. Based in Hong Kong and Shenzhen, we are at the heart of the world’s largest hub for lab-grown gemstones and jewelry manufacturing. Our location gives us unparalleled access to the most skilled artisans and advanced production techniques, ensuring every piece we create meets the highest standards of quality and design.
We connect the global supply chain deeply. Lab-grown gemstone production is dominated by a select few factories worldwide, and we have direct access to these sources, guaranteeing the best materials for our jewelry. Combined with decades of experience in crafting luxury pieces, our team delivers exquisite, custom designs that are both ethical and affordable.
