How to Tell Cubic Zirconia from Diamond?

Diamonds may be forever—but cubic zirconia (CZ) can give a dazzling first impression. If you're unsure whether a stone is a true diamond or a lookalike, you're not alone. At Little Treasury Jewelers, we often help clients sort out the subtle (and not-so-subtle) differences between the two.

Whether you’re browsing engagement rings or revisiting an older piece in your collection, here’s how to tell cubic zirconia from diamond—and why it matters.

What Is Cubic Zirconia, Exactly?

Cubic zirconia is a lab-created stone made from zirconium dioxide. It’s designed to simulate the look of a diamond but has very different properties in terms of brilliance, hardness, weight, and value. It’s commonly used in fashion jewelry and lower-cost alternatives to engagement rings.

Color: Usually flawless and colorless (even more so than most diamonds)
Origin: Always lab-made
Cost: Typically 10 to 20 times less than a comparable diamond

Cubic Zirconia vs. Diamond: The Key Differences

Let’s take a closer look at how diamonds and cubic zirconia compare across several key characteristics.

1. Light Performance

Diamond: Reflects light with crisp white flashes (brilliance) and subtle rainbow sparkle (fire)
CZ: Often looks glassy, with too much rainbow-like dispersion (a giveaway in bright light)

Diamonds sparkle with precision. CZ tends to have a softer, blurrier flash.

2. Surface and Wear

Diamond: The hardest natural material—rated 10 on the Mohs scale. Highly scratch-resistant and ideal for lifelong wear.
Cubic Zirconia: Softer (8 to 8.5), scratches more easily, and may dull over time with daily wear.

CZ is beautiful when new, but diamonds maintain their brilliance longer under regular use.

3. Heat Conductivity (How Professionals Tell the Difference)

Diamonds disperse heat quickly—CZ does not. That’s why thermal diamond testers can typically distinguish them.

At Little Treasury Jewelers, we go beyond the basics by using multi-mode testers that measure thermal and electrical conductivity, catching other simulants like moissanite, too.

4. Under Magnification

Even without high-end testing, a trained eye can often tell CZ and diamond apart:

CZ often shows:

Rounded facet junctions
Flow marks from the manufacturing process
Lack of natural inclusions

Diamond shows:

Sharp facet edges
Natural inclusions (carbon spots, feathers, crystals)
Unique growth patterns

Want to learn what your stone reveals under the microscope? We offer in-store evaluations and gemological consultations to help you understand exactly what you're looking at.

How to Tell if a Ring Is CZ or Diamond Without Tools

These easy checks may help—but aren’t conclusive:

The Fog Test: Breathe on the stone. If the fog dissipates instantly, it’s likely a diamond. If it lingers a few seconds, it could be CZ.
Newspaper/Text Test: Place the loose stone over printed text. If you can clearly read through it, it’s not a diamond.
Weight Test: CZ is heavier than diamond. If you’re comparing two same-size stones and one feels heavier, it may be CZ.

Still unsure? Bring it in. Our team will verify it for you with professional equipment.

Should I Buy CZ or Diamond?

It depends on what you’re looking for:

Cubic Zirconia: Great for fashion jewelry or temporary pieces where cost is a factor
Diamonds: Ideal for milestone moments, everyday wear, and heirloom-quality jewelry

At Little Treasury Jewelers, we offer both natural and lab-grown diamond options to meet every style, occasion, and budget—with expert guidance along the way.

Final Thoughts: Know What You’re Wearing

Distinguishing CZ from diamond isn’t just about price—it’s about performance, wearability, and meaning. When you choose a diamond from Little Treasury Jewelers, you’re investing in craftsmanship, care, and confidence that lasts for years.

Visit our showroom in Gambrills, MD, or contact us to schedule a diamond consultation.

Let us help you find brilliance that’s built to last.