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Lab-Grown Diamonds vs. Cubic Zirconia Stones: Key Differences You Need to Know

Lab-Grown Diamonds vs. Cubic Zirconia Stones: Key Differences You Need to Know

Here is a comparison table summarizing the key differences:


Lab-Grown Diamonds

Cubic Zirconia Stones


Pure carbon

Zirconium dioxide


10 (Hardest)

8 - 8.5


Exceptional brilliance and fire

Less intense sparkle


4Cs (like natural diamonds)

A - AAA proprietary scale


less than a mined diamond

less than a lab diamond

Best For

Durability, investment, authenticity

Affordability on a budget


Diamond jewelry is highly coveted for its brilliance, beauty, and status. As natural diamonds have become increasingly expensive, many consumers have turned to more affordable alternatives that look similar to the real thing. Two popular options are lab-grown diamonds and cubic zirconia. Though they may appear very similar at first glance, these two stones have several key differences.

This article will examine lab-grown diamonds and cubic zirconia, comparing them across various factors. We'll look at composition, hardness, sparkle, how they are graded, pricing differences, and more. By the end, you'll clearly understand how these two diamond simulants stack up. With this knowledge, you can better decide which stone fits your jewelry needs and budget when shopping.

What Is a Lab-Grown Diamond?

A lab-grown diamond, or a cultured or cultivated diamond, is a real diamond created inside a laboratory rather than within the earth. The process involves simulating the high heat and pressure conditions that form diamonds naturally underground. Small diamond seed crystals are placed in a growth chamber and gradually built up layer-by-layer using gases like methane or carbon dioxide.

While man-made, lab-grown diamonds have the same optical, chemical, thermal, and physical properties as mined diamonds. They test as real diamonds and comprise the same material - pure crystallized carbon. Well-grown lab diamonds are optically indistinguishable from natural diamonds, with the same sparkle and brilliance. The key difference lies in their origin of creation.

You can know more from here: What are Lab Grown Diamonds?

What Is a Cubic Zirconia Stone?

Cubic zirconia (CZ) is a synthetic diamond simulant designed to emulate a diamond's look. The material is zirconium dioxide rather than carbon, completely different from a diamond on a chemical composition level.

Natural zirconium dioxide is derived from mining the mineral baddeleyite. It is processed to form pure cubic zirconia crystals that mimic the optical properties of diamond. With a high refractive index, CZ can appear remarkably similar to diamonds in brilliance and fire.

The cubic zirconia was first synthesized in the 1970s and became popular as an affordable diamond alternative. It remains the most commonly purchased diamond simulant on the market today. The low cost and accessibility of CZ appeal to buyers who want the look of a large, dazzling gemstone on a budget.

Composition Comparison

The core composition is where lab-grown diamonds and cubic zirconia differ most significantly. A diamond is pure crystallized carbon, while CZ contains no carbon.

Lab-grown diamonds have the identical chemical makeup and atomic structure as natural diamonds since they both consist of carbon atoms arranged in the rigid cubic crystal system. They are both technically "diamonds" on a molecular level.

Cubic zirconia has a completely different chemical structure, composed of zirconium dioxide (ZrO2). Instead of carbon, its molecules contain zirconium and oxygen bonded together. It is a synthetic material formulated to simulate a diamond, not an actual diamond itself.

This underlying chemical variation impacts the two materials' durability, hardness, and physical performance. The carbon structure makes diamonds incredibly strong. The zirconium dioxide composition of CZ is relatively soft and brittle in comparison.

Hardness and Durability

The hardness of a gemstone determines its overall durability and resistance to wear and tear. The Mohs Scale ranks minerals by hardness, with diamonds graded at 10 - the highest on the scale. Their unparalleled hardness gives diamonds lasting longevity and keeps them from easily scratching.

Lab-created diamonds have virtually the same hardness as natural diamonds, rating 10 on the Mohs scale. They provide comparable durability and longevity, making them suitable for everyday wear.

Cubic zirconia is far below diamond on the Mohs scale, ranking at approximately 8 - 8.5. While still hard, CZ has substantially lower hardness than diamond. It is prone to abrasions and scratches over time. CZ jewelry requires more care and eventual replacement than diamond jewelry.

Lab-grown diamonds are the clear winner over softer cubic zirconia for long-lasting, durable jewelry that can withstand regular wear. Their superior hardness adds to their value and makes them a sound investment.

Sparkling Diamond Ring

Sparkle and Refractive Index

One of the most important factors in a diamond's beauty is its sparkle. Sparkle refers to the number of flashes of white light a diamond gives off. This light performance combines brilliance (internal light reflections) and fire (dispersion of spectral colors).

A diamond's refractive index - its ability to bend incoming light - largely determines the intensity of its sparkle. Diamonds have very high refractive indices of 2.417 - 2.419. This allows them to bend, reflect, and disperse light exceptionally well.

Lab-created diamonds display the same brilliant sparkle as natural diamonds. They have the same high refractive index and light performance. Well-cut lab diamonds exhibit a dazzling blaze of light with crisp flashes of fire and brilliance.

Cubic zirconia has a refractive index between 2.15 - 2.18. This is lower than diamond, so CZ does not sparkle quite as intensely. The flashes of light tend to have a more splintered, rainbow-like appearance. The sparkle is still bright and beautiful, but not to the degree of a diamond.

If maximizing sparkle is a priority, lab-grown diamonds are the better choice. They compete head-to-head with natural diamonds in light performance and brilliance.

Grading Scales

Diamonds are graded by gemologists on what is known as the 4Cs scale - Cut, Color, Clarity, and Carat weight. This universal grading system evaluates and ranks diamonds based on very specific criteria. It allows diamonds to be assessed independently and categorized accordingly.

Lab-grown diamonds are graded using the same 4Cs grading scale as natural diamonds. They receive grades for cut quality, color (lack of color), clarity (fewer imperfections), and carat weight. This allows them to be compared side-by-side to mined diamonds. Lab-grown diamonds generally have higher color and clarity grades than most mined diamonds.

Cubic zirconia is not graded on the diamond 4Cs scale because it has different material properties. Gemological labs have developed specific cubic zirconia grading scales based on their characteristics.

Most CZ is graded from A to AAA, with some lower-end graded CZ going down to B. The highest grade, AAAAA, is rare and signifies premium quality cubic zirconia with exceptional clarity and shine. Understanding the CZ grading system can help you select the best quality stone.

Because CZ and lab diamonds use different grading scales, they cannot be directly compared. It's an important distinction when choosing between the two.

Pricing Differences

Not surprisingly, the cost of lab-grown diamonds and cubic zirconia differ significantly. As lab diamonds have become more widely produced, prices have gone down. On average, you can expect to pay less for a lab diamond than a mined diamond of equivalent size and quality. With further advances in production technology, lab diamond prices will likely continue to decrease.

Cubic zirconia costs a fraction of both lab-grown and natural diamonds. Even high-quality AAA-grade CZ will generally be priced less than a similar lab diamond. For large carat weights, CZ can be cheaper. For those seeking an extremely affordable diamond-like stone, CZ provides impressive size and sparkle on a tight budget. Lab diamonds are better for those who prioritize authenticity, durability, and long-term investment.

diamond cubic zirconia

Visual Comparison

To the untrained eye, lab-grown diamonds and cubic zirconia can initially look quite similar, especially from a distance. Examining them side-by-side reveals noticeable differences upon closer inspection.

Some distinguishing characteristics to look for:

Comparison Factor Lab-Grown Diamond Cubic Zirconia
Sparkle Style Bright pinpoints of light Diffused, splintery sparkle
Color Near colorless Can have tints like gray, yellow, blue
Clarity Fewer inclusions Often grainy and visible inclusions
Facets Precise, geometric cuts Sometimes rounded or misshapen facets
Coatings None required Some are coated, coating can wear away
Overall Quality Refined, precision cutting and performance Lacks refinement of diamonds

    There are scenarios where a high-quality CZ could pass as a diamond without close examination. But side-by-side, cubic zirconia lacks the refinement, precision, and performance of real lab-grown diamonds.


    While they may appear similar, lab-grown diamonds and cubic zirconia are fundamentally different stones. Key distinctions include:

    • Composition: Lab diamonds are pure carbon, while CZ contains no carbon.
    • Hardness: Lab diamonds rate ten on the Mohs scale; CZ rates 8-8.5, making them softer and less durable.
    • Sparkle: Diamonds have superior brilliance and fire compared to CZ due to higher refractive index.
    • Grading: Diamonds are graded on the 4Cs scale, while CZ uses its grading system.
    • Cost: CZ is significantly cheaper than both lab-grown and natural diamonds.

    When shopping for diamond jewelry, it is important to understand what you are buying. Lab-grown diamonds offer an affordable, ethical alternative to mined diamonds without sacrificing quality or beauty. Cubic zirconia provides budget-friendly sparkle but lacks the real diamond's lasting value. Keep these key differences in mind, and you'll be equipped to select the right stone to fit your priorities and budget!

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