Jewelry Guide April 29, 2025

Will Moissanite Pass a Diamond Tester?

by Lisa Jewelry US 0 comments

I. Why This Question Matters

In recent years, moissanite has emerged as a popular alternative to diamonds, particularly among those seeking a brilliant, ethical, and affordable gemstone. However, for many prospective buyers, one of the most pressing questions remains: Will moissanite pass a diamond tester? The answer to this question is not as straightforward as it might seem, and understanding the intricacies of how diamond testers work is essential in gaining clarity on this issue.

Moissanite and diamond share many similar visual properties, especially their exceptional sparkle, but they differ in terms of chemical composition and thermal conductivity. For those unfamiliar with gemstone testing tools, the confusion surrounding this topic is understandable. The widespread use of diamond testers — commonly used by jewelers, consumers, and even in the resale market — has led to an increased focus on whether moissanite can be distinguished from diamonds through these devices.

II. What is a Diamond Tester and How Does It Work?

A diamond tester is a handheld electronic device used to identify diamonds and differentiate them from other gemstones based on their thermal conductivity. The key principle behind the diamond tester is that diamonds have an exceptionally high ability to conduct heat, far superior to most other materials. This property is what makes the device so effective at distinguishing diamonds from simulants or other natural stones.

How Does a Diamond Tester Work?

Diamond testers typically use a small probe that makes contact with the gemstone. The tester then heats the probe, which in turn causes the heat to travel through the stone. The device measures how quickly the heat is conducted through the gemstone, which provides a reading that helps to identify the stone’s authenticity.

High Thermal Conductivity of Diamonds: Diamonds are known for their superior thermal conductivity. This means they can rapidly dissipate heat, which is why when a diamond tester touches a diamond, the probe detects a fast transfer of heat, allowing it to register the stone as a diamond.

Moissanite’s Similar Thermal Conductivity: Surprisingly, moissanite has a very similar thermal conductivity to diamonds, meaning that when tested with a diamond tester, it can also conduct heat at a rate comparable to a diamond. This is the primary reason why moissanite can sometimes pass a diamond tester, even though it is not a diamond.

Despite moissanite’s ability to conduct heat at almost the same rate as diamonds, this test is not foolproof. A diamond tester cannot differentiate between a diamond and moissanite based solely on thermal conductivity, as the two materials share this key physical characteristic. However, while a diamond tester may not always distinguish the two, there are other properties and testing methods that jewelers and gemologists use to correctly identify them.

III. Moissanite’s Response to Diamond Testers: The Truth

Moissanite, despite being a brilliant and highly sought-after gemstone, is often mistaken for diamond due to its striking visual similarities. One of the primary reasons for this confusion is the way moissanite interacts with diamond testers. Understanding why moissanite passes or fails the diamond test is key to clearing up misconceptions and gaining a deeper understanding of the material properties that make these two gemstones unique.

Moissanite’s Thermal Conductivity: Almost the Same as Diamond

As mentioned earlier, diamond testers work by measuring the thermal conductivity of a gemstone. Diamonds are exceptional in this regard, with a thermal conductivity that is unmatched by most other stones. Moissanite, however, shares a similar property. It is a silicon carbide (SiC) gemstone, and silicon carbide itself is known for having a relatively high thermal conductivity, which is why it behaves similarly to diamond in a thermal conductivity test.

In fact, the thermal conductivity of moissanite is so close to that of diamonds that it often passes the initial diamond tester reading. This means that when a diamond tester is used, the probe detects heat transfer at nearly the same rate as it would for a diamond, leading to the conclusion that the gemstone is, in fact, a diamond.

What This Means for Moissanite Test Results

The reality is that moissanite can easily pass a diamond tester. This is because the tester is designed primarily to distinguish diamonds from simulants and less conductive materials. Since both diamonds and moissanite are highly conductive, the tester cannot distinguish between them based on this single property alone.

However, while moissanite’s ability to pass a diamond tester might suggest that it is equivalent to a diamond, this is far from the full picture. The key difference lies not in thermal conductivity, but in other physical and optical properties, such as refraction, dispersion, and hardness. These factors are not measured by a diamond tester, yet they are what ultimately set moissanite apart from diamonds.

Why Moissanite’s Test Results May Be Misleading

While the thermal conductivity of moissanite closely mimics that of a diamond, relying solely on a diamond tester to identify gemstones can be misleading. A diamond tester is simply one tool in a jeweler’s toolkit. It does not provide a complete picture of the gemstone’s true identity. To fully understand the differences between a diamond and moissanite, one must consider the broader range of physical properties that are not captured by the thermal conductivity test.

IV. Key Differences Between Moissanite and Diamond That a Tester Can’t Detect

Although a diamond tester may indicate that moissanite and diamond are similar based on their thermal conductivity, there are several critical differences between the two gemstones that are not detectable by a simple diamond tester. Understanding these differences is key to appreciating the unique characteristics of both stones and identifying them correctly in real-world situations.

1. Optical Properties: Fire and Brilliance

One of the most noticeable differences between diamonds and moissanite lies in their optical properties, particularly their fire (the dispersion of light into spectral colors) and brilliance (the overall sparkle and reflective quality). While both gemstones are known for their striking visual appeal, moissanite has a much higher dispersion than diamonds, meaning it refracts light into more vibrant rainbow-colored flashes.

Diamond Fire: Diamonds have a lower dispersion of light compared to moissanite, producing flashes of white light.

Moissanite Fire: Moissanite exhibits more colorful flashes due to its higher dispersion (around 0.104. compared to diamond’s 0.044). This results in a brighter and more colorful sparkle that can sometimes appear more intense than diamonds.

2. Refractive Index: The Sparkle Factor

The refractive index (RI) measures how much light is bent as it passes through a gemstone, which directly affects its sparkle and brilliance. Moissanite has a refractive index of 2.65–2.69. while diamonds have an RI of 2.42.

Moissanite’s Higher Refractive Index: This means moissanite bends light more intensely, contributing to its fiery, sparkling appearance.

Diamond’s Lower Refractive Index: While diamonds still sparkle beautifully, their lower RI results in a less dramatic visual effect than that of moissanite.

This difference can often be seen in the way light plays off the surface of the gemstone, particularly in well-lit environments or under direct light sources. While moissanite’s brilliance is more vibrant, diamond’s sparkle is characterized by a more subdued, classic glimmer.

3. Hardness and Durability

Both diamonds and moissanite are incredibly durable stones, but they differ slightly in terms of their hardness and resistance to scratches. A diamond, being the hardest known material on the Mohs scale, scores a perfect 10. while moissanite ranks slightly lower at 9.25.

Diamond’s Exceptional Hardness: Diamond’s perfect score on the Mohs scale means it is resistant to scratches and abrasions, making it an excellent choice for everyday wear.

Moissanite’s Slightly Lower Hardness: While moissanite is still extremely hard and durable, it is slightly less resistant to scratches than diamonds. However, this difference in hardness is minor and often unnoticeable to the average wearer.

Despite this, moissanite is still a highly durable stone that can withstand daily wear, making it a great option for engagement rings and other fine jewelry.

4. Price and Value

The price difference between moissanite and diamond is significant, and this is one of the most obvious distinctions between the two stones. While diamonds are considered rare and valuable, leading to high price points, moissanite is a lab-grown stone that is much more affordable.

Diamond’s High Value: Diamonds, due to their rarity, historical significance, and mining processes, carry a high price tag.

Moissanite’s Affordable Luxury: Moissanite offers a similar appearance to diamond at a fraction of the cost, making it an attractive option for those looking for luxury without the luxury price.

This price difference allows consumers to purchase larger stones with higher quality and clarity, making moissanite a popular choice for engagement rings and other fine jewelry pieces.

V. Can You Tell the Difference Between Moissanite and Diamond Without a Tester?

While a diamond tester can be helpful in distinguishing between diamonds and moissanite based on thermal conductivity, it does not account for several other critical factors that can help you identify the differences between these two gemstones without the use of any special tools. There are several ways to tell the difference between moissanite and diamond simply by visual inspection and professional equipment.

1. Visual Inspection: The Fire and Sparkle

One of the easiest ways to spot a moissanite versus a diamond is by examining the fire and sparkle of the stone. As mentioned earlier, moissanite has a much higher dispersion of light than diamonds, which leads to a more colorful flash or “fire.”

Moissanite’s Fire: Moissanite displays flashes of vibrant color — reds, greens, and blues — especially when it is exposed to bright light. This intense color dispersion is often more noticeable than that of diamonds.

Diamond’s Sparkle: Diamonds produce a classic white sparkle and are known for their clarity and brilliance. While diamonds do have fire, it is generally less pronounced than the colorful flashes seen in moissanite.

If you observe a gemstone closely under light, you might notice that a moissanite’s sparkle appears more intense and rainbow-colored, while the diamond’s sparkle is more subtle and white. This is a clear visual cue that can help you tell the two apart.

2. Refraction Test with Light

Another simple test involves using light to examine how the stone reflects and refracts light. You can shine a light on the gemstone and observe how the light bounces off the surface.

Moissanite: Due to its higher refractive index, moissanite will often exhibit a more vibrant and colorful reflection. The flashes of light you see will often be tinged with rainbow colors.

Diamond: Diamonds have a lower refractive index, so they will typically reflect light in a more subdued, clear manner. The reflection will tend to be more white and less colorful.

While this test might require a keen eye, it can be a useful indicator for distinguishing moissanite from diamonds.

3. Professional Tools for Identification

If you’re still uncertain, a professional jeweler can quickly identify whether a stone is a diamond or moissanite using more advanced tools, such as:

Loupe or Microscope: With a jeweler’s loupe or a microscope, they can examine the inclusions (internal characteristics) of the gemstone. Diamonds tend to have characteristic inclusions that moissanite typically does not possess.

Refractive Index Measurement: Jewelers also use refractive index measurement tools (like a refractometer) to differentiate between moissanite and diamond, as their refractive indices are different.

Heat Conductivity Test: While a standard diamond tester might not differentiate the two, advanced thermal conductivity testers might be used to observe even slight differences in heat transfer rates.

4. The Scratch Test (Hardness Test)

Diamonds are the hardest known material on the Mohs scale, scoring a 10. while moissanite, though still very durable, scores slightly lower at 9.25. Using a Mohs hardness scale tool, a professional could scratch the surface of the gemstone to assess its hardness.

Diamond: Will not be scratched by any material, including other diamonds.

Moissanite: While still highly resistant to scratching, it may show slight signs of wear when scratched by harder substances.

While this test is less commonly performed outside of professional settings, it’s another potential method for identifying the differences between the two.

Conclusion

Final Thoughts on Moissanite and Diamond Testers

In conclusion, the question of whether moissanite will pass a diamond tester is a nuanced one. While moissanite shares many physical properties with diamonds, particularly in terms of thermal conductivity, it is not a diamond. Diamond testers, which primarily assess thermal conductivity, cannot provide a complete picture of the gemstone’s identity. They may indicate that moissanite is a diamond because of its similar thermal properties, but they don’t account for the important differences in optical properties, refractive index, hardness, and price.

Ultimately, whether you choose a diamond or moissanite, knowing the true nature of your gemstone will allow you to appreciate it for what it truly is.