Distinguishing Natural and Synthetic Gems: A Guide for Gemologists

Distinguishing between natural and synthetic gems is a critical skill for gemologists. As the synthetic gem industry has grown dramatically over the past several decades, the ability to identify the telltale signs of lab-created stones has become increasingly important. In this comprehensive guide, we'll explore the various processes used to manufacture synthetic gems, the distinctive features that can help you identify them, and the history behind the development of modern gemology.

Basic Terminology

Before we dive into the details, let's establish some key terminology:

Natural Gems: Gems that form naturally within the Earth's crust, through geological processes.

Synthetic Gems: Gems that are duplicates of natural gems, grown in a laboratory setting.

Homocreates: Synthetic gem materials that have no natural counterparts.

Imitations: Gemstones or other materials that are presented as a different type of gem.

It's important to note that these definitions can sometimes overlap. For example, you may encounter a synthetic corundum stone that is being sold as an imitation aquamarine.

What to Look For First

When examining a gemstone, the first indication that you may be dealing with a synthetic rather than a natural gem is often the stone's clarity. Very fine clarity, to the point where no natural inclusions can be seen even with a loupe, is a strong clue that you're looking at a synthetic. However, this is not a foolproof test, as some synthetic gems can contain inclusions, while some natural gems may be exceptionally clean.

Another factor to consider is the stone's color. Synthetic gems are often designed to mimic the finest, most saturated natural colors. If you're examining a gem with a more modest color saturation, it's more likely to be natural.

A Brief History of Synthetic Gems

The development of modern gemology is closely tied to the history of synthetic gem production. Let's take a look at some key milestones:

The Beginning of Modern Gemology

The foundations of our understanding of gem chemistry, crystallography, and formation were laid in the 18th and 19th centuries. Landmark discoveries, such as Smithson Tennant's proof that diamond is made of carbon and Louis Vauquelin's demonstration that emerald and aquamarine are both beryls, paved the way for the classification of gems based on their chemical composition and mineral structure.

The First Synthetic Gems

In the late 19th century, a few scientists managed to synthesize minerals, but none were able to produce gem-quality stones. The first synthetic gems to reach the market were synthetic rubies, which appeared in 1885 and were sold as natural gems for as much as $2,500 per carat. Jewelers quickly noticed that these rubies contained bubbles, a feature never before seen in natural gems, sparking a controversy.

Gemstone Synthesis Expands and Improves

The 20th century saw a dramatic expansion and improvement in gem manufacturing. In the 1970s, existing processes were refined, and new synthetic gems, such as opal, turquoise, alexandrite, yttrium aluminum garnet (YAG), and gadolinium gallium garnet (GGG), were introduced. The former Soviet Union played a significant role in these advancements, particularly in the development of larger sizes and new colors of synthetic quartz.

Distinctive Features of Synthetic Gems

Now that we've covered the history, let's dive into the specific characteristics that can help you identify synthetic gems:

Flame Fusion Gems

Newer flame fusion gems are often very clean, requiring high magnification to distinguish them from their natural counterparts. Look for gas bubbles, which may appear singly, in clouds, or in cocoon shapes. Curved striae and curved color banding are also telltale signs of flame fusion stones, as these features are never found in natural gems.

Czochralski or Pulled Process Gems

Pulled gems are generally flawless, but they may contain gas bubbles, wispy smoke-like veils, curved striae, or curved color banding.

Skull Melt Gems

Although usually flawless, cubic zirconia (CZ) may contain gas bubbles, partially or completely filled with unmelted zirconium oxide powder. You can easily distinguish CZ from its singly refractive lookalikes by measuring its specific gravity.

Flux Grown Gems

Flux grown gems have clarity characteristics that closely resemble natural inclusions, so their identification requires careful examination. Under the loupe, you'll usually find straight growth lines and veil-like fingerprints. The flux veils differ from natural veils by having opaque, mostly white flux content, while natural veils are filled with transparent liquid or gas. Higher magnification may reveal hexagonal or triangular platelets, small crystals of platinum, chrysoberyl, or phenakite, which can be mistaken for natural hematite inclusions.

Hydrothermal Gems

Hydrothermal gems are the most challenging to distinguish, as the process so closely mimics nature. Their inclusions are often very similar to those found in natural gems. However, you may be able to spot straight growth characteristics, wispy veil-like inclusions that resemble fingerprints, and two-phase inclusions in parallel lines with a cottony appearance. Hydrothermal emeralds may also contain "spicules" or nail head inclusions, which are two-phase inclusions with conical tubes descending from phenakite crystals.

Mastering the ability to identify synthetic gems is a crucial skill for gemologists. By understanding the various manufacturing processes and the distinctive features they leave behind, you can confidently distinguish natural gems from their lab-created counterparts, ensuring the integrity of the gemstone trade.