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How to Identify Real Diamonds: International Standards from TGJTA Experts

Diamonds, the king of gemstones and the ultimate desire, are not only valuable but also symbols of strength and eternal beauty. As the Thai Gem and Jewelry Traders Association (TGJTA), we are committed to elevating industry knowledge to international standards. This article compiles essential techniques for identifying genuine diamonds, based on universal gemological principles. These methods, using your naked eye and a 10x Loupe—a vital tool for gem experts worldwide—will help you assess diamonds with greater confidence.


 

1. Naked-Eye Observations: Distinctive Brilliance and Fire

Before using any tools, international experts begin by observing the diamond with the naked eye. Genuine diamonds exhibit two prominent qualities:

  • Adamantine Luster: Real diamonds possess a surface that reflects light exceptionally well, resulting in a brilliant, sharp luster. In gemology, this is known as "Adamantine Luster," derived from the word "diamond" itself. This level of luster is rare in other gemstones and is a primary indicator of a diamond's authenticity.

  • Fire (Dispersion): When white light enters a diamond, it acts like a high-quality prism, splitting the light into spectral colors. This light then reflects back as flashes of various colors, a phenomenon called "Dispersion." Diamonds have very high dispersion, creating vibrant and distinct "fire," a captivating characteristic that most imitation stones cannot match.


 

2. Deeper Inspection with a 10x Loupe: Expert Techniques

A 10x magnifying loupe is the standard tool used by gem traders globally for quality assessment. Using a loupe allows us to see details invisible to the naked eye.

  • Facet Edge Sharpness: Due to the diamond's highest hardness on the Mohs scale (10), each facet edge is "razor-sharp" and virtually free from chips or scratches. If facet edges appear rounded, dull, or abraded, it may suggest the stone is not a real diamond.

  • Surface Condition: With its superior hardness, a diamond's surface is highly resistant to scratches. The facet surfaces should be perfectly smooth and free from any abrasions.

  • Absence of Doubling: This is a crucial technique. Diamonds are "singly refractive." When looking through the table facet down into the pavilion facets, the facet edges should appear as single, sharp lines. If you observe doubled or blurred facet edges, it indicates "double refraction," a key characteristic used to distinguish diamonds from many popular simulants.


 

3. Understanding Simulants: International Comparison Techniques

Familiarity with the properties of diamond simulants makes distinguishing natural diamonds easier.

  • Cubic Zirconia (CZ): While exhibiting brilliance and fire similar to diamonds, CZ is less hard (around 8.5), resulting in less sharp facet edges and a greater susceptibility to scratches. It also displays "extreme fire"—higher dispersion than diamond, leading to noticeably more intense rainbow flashes when compared side-by-side.

  • Synthetic Moissanite: Considered one of the closest simulants, it can sometimes confuse inexperienced individuals. However, moissanite is identifiable by:

    • Strong Double Refraction: Through a loupe, the pavilion facet edges will appear distinctly doubled, a characteristic entirely contrary to diamonds.

  • Synthetic Corundum & Spinel: Despite good hardness and luster, both have very low dispersion, lacking the characteristic "sparkle" of a diamond.

  • Glass: This is the easiest material to distinguish. With a low hardness of 5.5 on the Mohs scale, it scratches very easily. Facet edges are rounded and not sharp. Its luster and dispersion are significantly lower than a diamond's, resulting in minimal sparkle.


 

Identifying natural diamonds using these basic techniques requires practice and familiarity. Observing brilliance, fire, facet sharpness, and checking for double refraction with a loupe are all internationally recognized fundamental skills. However, for a 100% accurate and complete assessment, it is recommended to consult a professional gemologist or a trusted laboratory equipped with advanced tools such as microscopes, refractometers, specific gravity testers, and CVD screening devices.

The Thai Gem and Jewelry Traders Association (TGJTA) hopes this information is beneficial and helps enhance the confidence of both industry professionals and consumers in selecting and acquiring these precious gemstones.

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