How to tell the Difference between Crystal and Diamond?

At Greis Jewelers, we take pride in guiding our customers through the jewelry selection process, ensuring they find the perfect piece that matches their style and preferences. Our experienced team helps customers identify the key differences between materials like crystal and diamond, empowering them to make informed decisions. Here’s a closer look at how to distinguish between crystal and diamond, from simple at-home tests that anyone can do to the more technical methods used by professional jewelers.

Everyday Ways to Tell the Difference Between Crystal and Diamond

1. The Scratch Test

One of the simplest ways to tell whether a gemstone is a diamond or a crystal is the scratch test, which takes advantage of each material’s hardness.

  • Diamonds: Diamonds rank a 10 on the Mohs scale of hardness, making them the hardest naturally occurring substance on Earth. This means they can easily scratch glass and other hard surfaces without sustaining any damage.
  • Crystals: Crystals like quartz or cubic zirconia are much softer, ranking between 6 and 8.5 on the Mohs scale. If you lightly scratch a crystal on glass, it may leave a faint mark, but the crystal itself could show signs of wear.
  • At-Home Tip: Try gently scratching a glass surface with your stone (though this should be done carefully to avoid damaging anything valuable). If the stone scratches the glass effortlessly, it’s likely a diamond.

2. The Fog Test

A quick and easy test you can perform anywhere is the fog test.

  • Diamonds: Diamonds are excellent at dispersing heat. If you breathe on a diamond, the fog from your breath should dissipate almost instantly, leaving the stone clear.
  • Crystals: Crystals like cubic zirconia or glass do not disperse heat as efficiently. When you breathe on a crystal, the fog will linger for several seconds before disappearing.
  • At-Home Tip: Hold the gemstone close to your mouth and exhale onto it. If the fog clears right away, you may have a diamond; if it lingers, it’s more likely to be a crystal.

3. Weight Comparison

Another noticeable difference between diamonds and crystals is their weight.

  • Diamonds: Diamonds are denser and heavier than crystals of the same size.
  • Crystals: Crystals like cubic zirconia tend to be lighter, so if a stone feels lighter than expected for its size, it could be a crystal.
  • At-Home Tip: Hold two stones of similar size—if one feels significantly lighter, it may be a crystal.

Visual Differences: Appearance Under Close Inspection

1. Brilliance and Sparkle

The way a gemstone reflects light is one of the most striking visual differences between diamonds and crystals.

  • Diamonds: Due to their unique structure, diamonds have a higher refractive index, allowing them to sparkle more intensely and produce flashes of rainbow colors (also known as fire). Diamonds exhibit both brilliance (white light reflection) and fire.
  • Crystals: Crystals such as cubic zirconia can sparkle but typically have a more glassy appearance. They may lack the depth and vibrant play of colors found in diamonds.
  • Jeweler’s Tip: Look at the stone under natural light. A diamond’s fire and brilliance should be more vivid than that of a crystal, which will have a simpler, less dynamic reflection of light.

2. Clarity

Clarity refers to the presence of inclusions—tiny imperfections within the stone.

  • Diamonds: Most diamonds contain some natural inclusions, though high-quality diamonds have fewer visible imperfections. These inclusions often give diamonds a unique appearance under magnification.
  • Crystals: Synthetic crystals like cubic zirconia or Swarovski crystals are typically flawless, as they are manufactured to perfection. The absence of inclusions may indicate that the stone is not a diamond.
  • Jeweler’s Tip: Using a jeweler’s loupe or magnifying glass, check the stone for small inclusions. A diamond will usually show some, whereas a crystal will appear too perfect.

Technical Methods for Identifying Crystal vs. Diamond

When more precision is needed, jewelers use technical methods to differentiate between crystal and diamond. Here are some of the most common:

1. Refractive Index (RI) Measurement

A refractometer measures how much light bends when entering a gemstone, which can help distinguish between materials.

  • Diamonds: Diamonds have a high refractive index of 2.42, which contributes to their brilliance and fire.
  • Crystals: Crystals like cubic zirconia have a lower RI, usually around 2.15 to 2.18.
  • Jeweler’s Tip: Measuring the refractive index of a stone will quickly indicate whether it's a diamond or a crystal.

2. Thermal Conductivity Test

A thermal conductivity tester, also known as a diamond tester, can easily differentiate between a diamond and a crystal by measuring how quickly heat passes through the stone.

  • Diamonds: As excellent conductors of heat, diamonds allow heat to pass through them almost instantly.
  • Crystals: Crystals are poor conductors of heat, so a diamond tester will indicate that they are not diamonds.
  • Jeweler’s Tip: A professional jeweler can use a thermal conductivity tester to verify whether your stone is a diamond or a crystal within seconds.

Color and Fluorescence

Some stones can be identified by examining their color and fluorescence under UV light.

  • Diamonds: Many diamonds will fluoresce a blue color under ultraviolet (UV) light, though not all diamonds have this characteristic.
  • Crystals: Crystals like cubic zirconia or other synthetics typically do not fluoresce or may fluoresce in different colors, such as yellow or green.
  • Jeweler’s Tip: If available, viewing the stone under UV light can offer another clue to its identity.

Conclusion: Crystal vs. Diamond—Spotting the Differences

While diamonds and crystals may seem similar at first glance, there are clear differences in terms of brilliance, hardness, and overall value. Knowing how to tell them apart—whether through simple at-home tests or by seeking professional assistance—will ensure that you make a confident and informed decision when purchasing fine jewelry.

At Greis Jewelers, we are committed to offering only the finest quality diamonds, and our expert team is here to guide you through the process of selecting the perfect piece. Whether you’re choosing between a diamond or crystal, our experienced staff will help you determine which is right for your needs and budget.

Visit Greis Jewelers today to explore our collection of diamonds and gemstones or speak with one of our experts for professional advice on choosing the perfect stone.