Will Cubic Zirconia Pass a Diamond Tester?

For consumers and jewelry enthusiasts alike, distinguishing between genuine diamonds and their more affordable counterparts is a critical skill. Among diamond simulants, cubic zirconia (CZ) stands as one of the most popular alternatives, offering impressive sparkle at a fraction of the price. But as technology advances and testing methods become more accessible, a common question emerges: Will cubic zirconia pass a diamond tester?

Understanding Diamond Testers

Before addressing this question directly, it's important to understand how diamond testers work. Traditional diamond testers operate on a simple principle: they measure thermal conductivity. Diamonds possess exceptional thermal conductivity properties, allowing heat to pass through them quickly. Most basic diamond testers are designed to detect this specific property.

There are primarily two types of testers commonly used:

1. Thermal conductivity testers: These measure how quickly heat disperses through the material.
2. Electrical conductivity testers: These measure how well the material conducts electricity.
3. Dual testers: These combine both thermal and electrical conductivity tests for greater accuracy.

Cubic Zirconia: The Popular Diamond Simulant

Cubic zirconia is a synthesized material made from zirconium dioxide. When properly cut, it exhibits many visually appealing characteristics similar to diamonds:

• Excellent clarity
• High refractive index producing significant brilliance
• Durability (8.5 on the Mohs hardness scale, compared to diamond's 10)
• Colorless appearance (though it can be manufactured in various colors)

These qualities make CZ an attractive and budget-friendly alternative to natural diamonds. However, despite these visual similarities, the physical properties of cubic zirconia differ significantly from those of diamonds at the molecular level.

The Verdict: Will Cubic Zirconia Pass a Diamond Tester?

No, cubic zirconia will not pass a properly functioning diamond tester.

The reason is straightforward: cubic zirconia has dramatically different thermal conductivity properties compared to diamonds. While diamonds rapidly conduct heat, cubic zirconia is a thermal insulator, meaning it conducts heat poorly. This fundamental difference allows even basic thermal diamond testers to distinguish between the two materials reliably.

When a diamond tester is applied to cubic zirconia:

• Thermal conductivity testers will register a negative result
• Electrical conductivity testers will also show different readings than with diamonds
• Dual testers will easily identify the stone as something other than diamond

Other Methods to Distinguish CZ from Diamonds

Beyond electronic testers, there are several other methods professionals and consumers use to tell cubic zirconia apart from diamonds:

Visual Inspection

1. Weight: Cubic zirconia is approximately 1.7 times heavier than a diamond of equivalent size. A 1-carat CZ will appear smaller than a 1-carat diamond.

2. Dispersion (Fire): CZ actually displays more "fire" (the rainbow effect when light hits the stone) than diamonds. This excessive rainbow effect can be a telltale sign of cubic zirconia.

3. Flaws: Naturally occurring diamonds typically contain microscopic inclusions. Laboratory-created cubic zirconia is usually flawless, sometimes appearing "too perfect" compared to most natural diamonds.

4. Facet Edges: Under magnification, CZ often shows slightly rounded facet edges compared to the sharp edges of diamond facets.

Simple Tests

1. Breath Test: Due to the difference in thermal conductivity, a diamond will remain clear when breathed upon, while the fog from your breath will linger longer on cubic zirconia.

2. Newspaper Test: Place the stone face-down on a newspaper. If you can read the print through the stone, it's likely not a diamond. Diamonds refract light so strongly that text becomes illegible when viewed through them.

3. UV Light Test: Many (though not all) diamonds will fluoresce under ultraviolet light, while cubic zirconia typically does not.

Modern Testing Challenges

As technology advances, so too do the methods for creating increasingly sophisticated diamond simulants. While cubic zirconia cannot fool standard diamond testers, newer synthetic diamond alternatives like moissanite can sometimes register false positives on basic thermal testers.

This is why jewelry professionals often use multiple testing methods and more advanced tools like spectroscopes and multi-property testers to definitively identify gemstones. For consumers concerned about authentication, professional jewelers or gemologists can provide conclusive identification services.

Why This Matters

The distinction between cubic zirconia and diamonds has significant implications:

• Financial: Diamonds retain considerable value, while cubic zirconia has minimal resale value.
• Insurance: Insurance coverage for fine jewelry often requires proper identification and appraisal.
• Emotional Value: For significant purchases like engagement rings, knowing exactly what you're buying supports informed decision-making.
• Ethical Considerations: Some consumers specifically choose cubic zirconia or other alternatives to avoid concerns associated with diamond mining.

Conclusion

While cubic zirconia offers an affordable alternative with impressive visual qualities, it cannot pass a properly functioning diamond tester due to its fundamentally different physical properties. This is actually good news for consumers, as it means relatively inexpensive and accessible testing methods can help verify whether that stunning stone is a diamond or a simulant.

Whether you're purchasing new jewelry, inheriting family heirlooms, or considering the sale of existing pieces, understanding the limitations of cubic zirconia when subjected to diamond testing provides valuable knowledge for making informed decisions about your jewelry collection.

For definitive identification, particularly for high-value items, consulting with a certified gemologist remains the most reliable approach.