Cubic Zirconica

Distinguishing Real Diamonds from Cubic Zirconias: A Comprehensive Guide

Posted by Matt Anton

Distinguishing Real Diamonds from Cubic Zirconias: A Comprehensive Guide

Are you in the market for a stunning piece of jewelry, but you want to be absolutely sure of its authenticity? Distinguishing between real diamonds and cubic zirconias can be quite the challenge, as these two gemstones share a striking resemblance. In this comprehensive guide, we will explore the various aspects that set these two stones apart, enabling you to make an informed choice when it comes to your precious jewelry investments.

The Basics: What Are Diamonds and Cubic Zirconias?

Before delving into the differences, it’s essential to understand the basics of these two gemstones.


  • Diamonds are naturally occurring gemstones formed deep within the Earth’s mantle over millions of years.
  • They are renowned for their exceptional hardness, making them one of the hardest substances on Earth.
  • Diamonds are prized for their brilliance, sparkle, and fire, which result from their ability to refract and disperse light.

Cubic Zirconias:

  • Cubic zirconias are synthetic gemstones created in a laboratory setting.
  • They are optically flawless and exhibit remarkable brilliance, similar to real diamonds.
  • Cubic zirconias are more affordable than genuine diamonds, making them a popular alternative for jewelry.

Physical Properties: The Telltale Signs


  • Diamonds score a perfect 10 on the Mohs scale of mineral hardness, making them extremely resistant to scratching.
  • Cubic zirconias are softer, with a hardness rating of approximately 8-8.5, making them more susceptible to scratches.

2. Dispersion and Fire:

  • Diamonds have a high dispersion rate, which is responsible for their colorful play of light, often referred to as “fire.”
  • Cubic zirconias also exhibit fire, but it may be even more pronounced than in diamonds due to their higher refractive index.

Visual Examination: What to Look For


  • Diamonds typically have a slightly lower brilliance than cubic zirconias.
  • In diamonds, you might notice subtle flashes of colored light, whereas cubic zirconias often emit white flashes.


  • Diamonds may contain internal flaws or inclusions, which are often not visible to the naked eye.
  • Cubic zirconias are virtually flawless under magnification, lacking the natural inclusions found in diamonds.

Professional Gemological Testing

For a definitive answer, consider professional gemological testing, which involves:

Thermal Conductivity:

  • Diamonds are excellent conductors of heat, so a diamond tester will quickly disperse heat.
  • Cubic zirconias are poor conductors, causing the heat to disperse more slowly.

Refractive Index:

  • Gemologists use a refractometer to measure a gemstone’s refractive index. Diamonds have a lower index compared to cubic zirconias.

The Bottom Line

Distinguishing real diamonds from cubic zirconias requires a keen eye, an understanding of their properties, and sometimes professional assessment. While each method discussed here offers clues, a combination of visual inspection and gemological testing is the most reliable way to ensure the authenticity of your gemstone. So, whether you’re shopping for an engagement ring or a beautiful necklace, armed with this knowledge, you can confidently make the right choice for your jewelry collection.

Distinguishing Real Diamonds from Cubic Zirconias: A Comprehensive Guide was last modified: November 20th, 2023 by Matt Anton