How to Tell Diamond vs Moissanite: A Guide

Diamonds and moissanites are both popular choices for jewelry, especially engagement rings, due to their brilliance and durability. However, while they may appear similar at first glance, there are distinct differences between the two gemstones. Whether you’re a jeweler, a buyer, or just curious, this guide will help you identify and differentiate between a diamond and a moissanite.

1. Brilliance and Sparkle

• Moissanite:

  • Brilliance: Moissanite is known for its intense brilliance, often producing a "rainbow" effect due to its higher refractive index (2.65 – 2.69). This means it bends light more than a diamond does, resulting in a flashier, more colorful sparkle.
  • Key Identifier: Look for the "fire" or colorful flashes of light when viewed under direct lighting. Moissanite often has more noticeable rainbow effects compared to diamonds.

• Diamond:

  • Brilliance: Diamonds have a lower refractive index (2.42), giving them a more subtle sparkle that typically appears as white light. This classic brilliance is what makes diamonds so prized.
  • Key Identifier: Diamonds sparkle in a more understated way, with less colorful flashes and more consistent white light reflection.

2. Hardness and Durability

• Moissanite:

  • Hardness: Moissanite ranks 9.25 on the Mohs scale of hardness, making it one of the hardest gemstones, though slightly less hard than diamonds.
  • Durability: While extremely durable and scratch-resistant, moissanite can be distinguished from diamonds by testing its resistance to scratches using a harder material.

• Diamond:

  • Hardness: Diamonds rank 10 on the Mohs scale, making them the hardest known natural material. They can scratch almost any other substance, including moissanite.
  • Durability: Because of its unmatched hardness, a diamond is less prone to scratching and can be tested for its superior durability.

3. Weight and Density

• Moissanite:

  • Density: Moissanite is less dense than a diamond. If you were to place a moissanite and a diamond of the same size on a scale, the moissanite would weigh slightly less.
  • Key Identifier: Professional jewelers can use this difference in density to differentiate between the two stones using a specific gravity test or by comparing them on a finely tuned scale.

• Diamond:

  • Density: Diamonds are denser and will weigh more than moissanite of the same size.
  • Key Identifier: If you have access to the tools, compare the weights of the two stones.

4. Heat Conductivity

• Moissanite:

  • Heat Conductivity: Moissanite and diamonds both conduct heat well, but moissanite has a slightly lower thermal conductivity than diamonds. This makes traditional thermal conductivity testers (often called diamond testers) less effective at differentiating between the two.
  • Key Identifier: More advanced devices, known as "moissanite testers," are designed to detect the subtle differences in thermal conductivity between moissanite and diamonds.

• Diamond:

  • Heat Conductivity: Diamonds have a high thermal conductivity, making them easily identifiable with a traditional diamond tester, though these tools can sometimes mistake moissanite for a diamond due to their similar properties.

5. Visual Inclusions and Birefringence

• Moissanite:

  • Birefringence: Moissanite is doubly refractive, meaning light passes through it in two different directions. This can create a "double vision" effect when you look at the facets of the stone through a loupe.
  • Key Identifier: View the stone from the side using a jeweler’s loupe. If you see doubled facets, it’s likely a moissanite.

• Diamond:

  • Birefringence: Diamonds are singly refractive, meaning light passes through them in a single direction, without the doubling effect seen in moissanite.
  • Key Identifier: A lack of doubled facets under magnification suggests the stone is a diamond.

6. Price

• Moissanite:

  • Cost: Moissanite is significantly less expensive than diamonds, even for stones of similar size and quality. This can be a key indicator when comparing two stones.

• Diamond:

  • Cost: Diamonds are generally much more expensive due to their rarity and the value placed on them in the market.

Conclusion

While moissanite and diamonds can look very similar, they have distinct differences that can be identified through careful observation and testing. Moissanite is known for its intense brilliance and affordability, making it an attractive alternative to diamonds. On the other hand, diamonds are valued for their classic sparkle, unparalleled hardness, and traditional significance.

Whether you’re choosing between the two for an engagement ring or simply want to tell them apart, understanding these differences will help you make an informed decision or accurate identification.