how to recognize gemstones

In the world of jewelry and gemstone collecting, the ability to recognize genuine, natural gemstones is a valuable skill. With the increasing prevalence of synthetic and treated stones, it's essential to be able to distinguish the real from the imitation. In this comprehensive guide, we'll explore the key characteristics and techniques that will help you confidently identify genuine gemstones.

Understanding Gemstone Formation and Properties

Gemstones are naturally occurring crystalline minerals that form deep within the Earth's crust and mantle. The unique conditions of temperature, pressure, and chemical composition give rise to the diverse array of gemstones we see today. Each type of gemstone has its own distinct physical and optical properties, which serve as the foundation for identification.

Hardness and Toughness

One of the primary characteristics to consider when identifying a gemstone is its hardness. The Mohs hardness scale, developed by the German mineralogist Friedrich Mohs, ranges from 1 (the softest) to 10 (the hardest). Diamonds, for example, rank at 10 on the Mohs scale, making them the hardest known natural material. In contrast, softer gemstones like talc and gypsum fall on the lower end of the scale.

Toughness, on the other hand, refers to a gemstone's resistance to chipping, cracking, or breaking. While hardness and toughness are related, they are not the same. Some gemstones, like quartz, are relatively hard but can be brittle, while others, like corundum (the mineral that includes rubies and sapphires), are both hard and tough.

Refractive Index and Dispersion

The refractive index of a gemstone is a measure of how much the speed of light is reduced as it passes through the material. This property is responsible for the gemstone's ability to bend and refract light, creating the characteristic "fire" and "brilliance" we associate with many gems. Each type of gemstone has a unique refractive index, which can be used as a diagnostic tool in identification.

Dispersion, on the other hand, refers to the ability of a gemstone to split white light into its component colors, creating the rainbow-like effect known as "fire." Diamonds, for example, have a high dispersion, which is why they exhibit such intense fire and brilliance.

Color and Pleochroism

Color is perhaps the most obvious and recognizable characteristic of a gemstone. Gemstones can exhibit a wide range of colors, from the deep red of rubies to the vibrant green of emeralds. The color of a gemstone is determined by its chemical composition and the presence of trace elements within the crystal structure.

Pleochroism is the ability of a gemstone to display different colors when viewed from different angles. This property is particularly noticeable in gemstones like iolite, which can appear blue, violet, or gray depending on the viewing angle.

Identifying Genuine Gemstones

Now that we've covered the fundamental properties of gemstones, let's dive into the practical steps you can take to identify genuine, natural gems.

Visual Inspection

The first step in gemstone identification is a thorough visual inspection. Look for the following characteristics:

• Inclusions: Natural gemstones often contain small inclusions, such as air bubbles, mineral deposits, or fractures, within their crystal structure. These inclusions can be used as a "fingerprint" to distinguish natural gems from synthetic or treated stones.
• Symmetry and Proportions: Genuine gemstones typically exhibit a high degree of symmetry and consistent proportions, as they are formed under natural conditions. Irregularities or inconsistencies in the shape and size of the gem may indicate a synthetic or treated stone.
• Surface Characteristics: Natural gemstones often have a slightly uneven or textured surface, while synthetic stones may have a more uniform, flawless appearance.

Hardness and Specific Gravity Testing

As mentioned earlier, the hardness of a gemstone is a key identifying characteristic. You can perform a simple hardness test using the Mohs scale and common household items, such as a steel file or a piece of quartz. Gently scratch the surface of the gemstone and compare the results to the Mohs scale to determine its hardness.

Specific gravity, which is the ratio of a gemstone's weight to the weight of an equal volume of water, is another useful property for identification. You can measure the specific gravity of a gemstone using a jeweler's scale and a container of water.

Optical Properties

Examining the optical properties of a gemstone can provide valuable clues to its identity. You can use a gemological microscope or a loupe to observe the gemstone's refractive index, dispersion, and pleochroism.

For example, a gemstone with a high refractive index and strong dispersion is likely a diamond, while a gemstone with pronounced pleochroism may be a corundum (ruby or sapphire) or iolite.

Advanced Gemological Testing

In some cases, more advanced gemological testing may be necessary to conclusively identify a gemstone. This can include techniques such as:

• X-ray Fluorescence (XRF): This non-destructive analysis method can provide information about the chemical composition of a gemstone, helping to distinguish between natural and synthetic varieties.
• Spectroscopy: By analyzing the absorption and emission spectra of a gemstone, gemologists can identify the presence of specific elements and impurities, which can be used to determine the gemstone's identity.
• Thermal Testing: Observing a gemstone's reaction to heat can provide clues about its composition and origin.

These advanced techniques are typically performed by professional gemologists in specialized laboratories.

Conclusion

Recognizing genuine, natural gemstones requires a combination of knowledge, observation, and testing. By understanding the fundamental properties of gemstones and mastering the techniques for identification, you can confidently navigate the world of fine jewelry and gemstone collecting. Remember, the more you learn about gemstones, the better equipped you'll be to appreciate the true beauty and value of these natural wonders.