How To Tell Cubic Zirconia From Diamond – A Complete Guide

It is identical at first glance, with cubic zirconia being a diamond simulant that almost inseparably resembles its natural counterpart. However, diamond reigns supreme in terms of rarity, exclusivity, and value, with CZ steadily growing in popularity as a cost-effective alternative, a certain glittery appearance at a fraction of the price. But how can you spot these stones' differences, especially when cubic zirconia can look so close to the real thing? 

This guide will walk you through key differences, easy tests, and expert recommendations to help you identify whether that dazzling gem is a genuine diamond or a cubic zirconia.

What Are Diamonds and Cubic Zirconia?

The stakes are quite high when it comes to distinguishing between CZs and diamonds. Whether you're shopping for an engagement ring, a family heirloom, or a gift for a special occasion, knowing what you're buying ensures clarity and confidence in your purchase.

Knowing the stone type is critical for appraisals and accurate valuations, whether for collectors or specialists. It also helps jewelers recommend the best action, even for simple jewelry repairs or upgrades.

At LA Chic Jewelry, based in Los Angeles and backed by three generations of craftsmanship, we pride ourselves on helping customers confidently choose the right stones—especially in the world of high-quality, AAA-certified CZ.

Now, let's move on to how to tell cubic zirconia from a diamond.

Key Differences Between Cubic Zirconia and Diamond

1. Brilliance and Fire

• Diamond: The extent to which white light is reflected from a gemstone is called brilliance. Fire here refers to the dispersion of colored light. Diamonds are known for their unmatched brilliance and balanced fire, giving them a sharp and vivid sparkle.

The natural gemstone, therefore, has a mix of white light (brilliance) and colored flashes (fire). The sparkle is sharp and intense.

• Cubic Zirconia: Cubic zirconia glows with a “rainbow-like” effect, considering its higher dispersion rate. This creates a more iridescent sparkle that lacks the subtlety and depth of a real diamond. 

The bedazzling appearance with a striking sparkle may appear “too perfect” to the trained eye. CZ is a giveaway in certain lighting conditions.

Looking for dazzling sparkles without the high price tag? Explore our AAA-certified CZ collection at LA Chic Jewelry, where elegance meets affordability.

A quick tip: View the stone under natural light. Diamond brilliance is crisp, while CZ may appear overly colorful or shiny.

2. Hardness and Durability

On the Mohs scale of hardness:

• Diamonds: Rank 10, making them impervious to scratches and damage for everyday wear. Natural gemstones formed deep within Earth under extreme heat and pressure are incredibly durable and ideal for lifelong jewelry pieces. Diamonds typically contain natural inclusions or imperfections, which add to their uniqueness and can affect their value. 

• Cubic Zirconia: Ranks at 8–8.5, softer and more prone to scratches, chips, or clouding over time. CZ is created in lab-controlled environments and is almost perfect, without any visible inclusions or imperfections. 

A more versatile, ethical, and affordable choice for everyday wear and fashion jewelry, these perfectly resemble diamonds with flawless clarity and intense rainbow sparkle. 

At LA Chic Jewelry, we offer expertly crafted CZ engagement rings designed to stand the test of time—with a look and feel that rivals the real thing.

A quick tip: Check the surface clarity. Diamonds have superior resilience, maintaining their luster without visible wear.

3. Weight

• Diamonds: These are naturally lightweight compared to many other gemstones, including cubic zirconia. A 1-carat diamond has a relatively lower density, which means it will feel lighter when held or worn. This lighter weight is part of what gives diamonds their delicate elegance and makes them comfortable for everyday jewelry, especially rings and earrings. 

When comparing two stones of identical size, a genuine diamond will feel noticeably lighter than its cubic zirconia counterpart, even if both are visually the same.

• Cubic Zirconia: Cubic zirconia is significantly denser than diamond, which gives it a heavier feel when matched in size. A 1-carat CZ stone will feel around 50% heavier than a 1-carat diamond. 

Because of this density difference, CZ stones are usually measured by millimeter size rather than carat weight. The added weight doesn't affect the appearance, but it can be a subtle clue when trying to tell the two apart—especially in larger jewelry pieces where the heaviness is more noticeable to the touch.

Quick tip: Hold the stone in your hand. A noticeably heavy feel relative to its size could signal cubic zirconia.

4. Clarity

• Diamond: Diamonds formed deep beneath the Earth, and so because of this, they have inclusions. From those tiny imperfections to those flaws, these flaws are part of what makes the diamond unique—being graded on a scale from Flawless (FL) to Included (I) by gemological standards. 

With these exclusive high-clarity diamonds, most commercial diamonds fall in the middle of this scale. Though reducing the diamond’s brilliance, these also confirm its authenticity as a natural gemstone. 

• Cubic Zirconia: On the contrary, Cubic zirconia is virtually flawless and lab-created under controlled environments. Since formed under controlled conditions, CZ stones are free from inclusions or blemishes, often achieving Flawless (FL) to Internally Flawless (IF) clarity levels. 

Their high clarity enhances the stone's sparkle and brilliance, sometimes making it appear more radiant than a natural diamond. Authenticity here is, however, under question, which may raise suspicion. 

Protip: 

If you want flawless clarity and a bold, radiant finish, LA Chic Jewelry's custom CZ designs offer a luxurious look without compromise.

5. Heat Conductivity

• Diamond: The best thermal conductors in nature, high heat conductivity refers to a high heat dispersion. Heat dispersion is one property that is used to identify authentic diamonds. 

When a real diamond is exposed to warmth, it is cool to the touch because it does not have the quality to retain heat. Professional jewelers use a diamond tester that measures heat conductivity—if the stone conducts heat well, it’s likely a genuine diamond. 

• Cubic Zirconia: Cubic Zirconia, on the contrary, is a thermal insulator, meaning it does not conduct heat effectively. When subjected to warmth or breath (such as in the fog test), CZ stones retain heat and fog more easily and for longer than diamonds. 

6. Cost

• Diamond: Diamonds are the most expensive naturally occurring gemstones in the market, with their price ranges being influenced by the 4Cs: cut, color, clarity, and carat weight. Here, a high-quality diamond costs nearly thousands of dollars per carat, thus becoming a significant source of investment. 

From their rarity to exclusivity and dominating cultural status, diamonds contribute to pure luxury due to their premium pricing range. 

• Cubic Zirconia: CZ, a cost-effective diamond alternative, imitates diamonds and is also known as the synthetic counterparts, offering a similar look as diamonds but at a fraction of the cost. 

A CZ stone of similar size and appearance to a diamond might cost under $100, compared to several thousand for a real diamond.

At-Home Tests to Try

If you don’t have access to expert tools, here are a few easy DIY tests you can perform:

1. Fog Test 

Breathe heavily two or three times on a diamond, similar to what you do on a mirror. A diamond appearing with a superior thermal conductivity won’t retain but quickly disperse the fog. CZ, in contrast, will hold the mist for a few seconds. This development can be attributed to a simple at-home test that helps differentiate a diamond and CZ. 

The fog test for the best results should be performed at room temperature, with the reaction being repeated a few times to gain consistency.

2.  Scratch Test

The process involves scratching the stone against a material. For instance, we use a softer material here, such as to lightly scratch the surface of the gemstone, to observe how the stone reacts when scratched against the material. Since diamonds form the hardest known substance, they won’t scratch or show wear when rubbed against glass.

CZ, while still relatively hard (8–8.5 on the Mohs scale), but not as durable as a diamond, will show minor scratches when subjected to the same test. 

3. Newspaper Test

The newspaper test involves a special visual method to distinguish a diamond from CZ based on how the stone reacts. Place a flat side of the stone on the newspaper, or printed text. Looking at the diamond, you won’t be able to read through the stone. The refractive index is high, and the scattered and blending of light is so intense that the text becomes blurred. 

CZ, in contrast, features a lower refractive index and hence allows more light to pass through it. The result is that you can see and, therefore, read them more clearly. The test works perfectly fine on loose, well-cut stones. 

4. UV Light Test

The UV light test is a quick way to differentiate between a diamond and cubic zirconia based on how each reacts to ultraviolet (UV) light. This is the blacklight test, wherein the gemstone is placed under a blacklight under which these natural gemstones emit a blue fluorescence light whose intensity keeps on varying. 

Many diamonds may not possibly show fluorescence at all. CZ, on the contrary, glows as a yellow, green, or white hue. 

When in Doubt, Consult an Expert

If you’re still uncertain after performing these checks, it’s always best to consult a professional jeweler. A certified appraiser can evaluate the stone with tools like microscopes, refractometers, and thermal conductivity testers, giving you unequivocal answers.

At LA Chic Jewelry, we specialize in diamond expertise and ensure you feel confident and informed about your jewelry choices. Whether you're considering a purchase, appraisal, or upgrade, our team guides you every step of the way. Throughout our 35-year history, we've specialized in high-quality AAA-certified Cubic Zirconia products, with a special love for engagement and custom rings.