The Rise of Laboratory-Grown Gems

As technology has advanced, the ability to replicate the Earth's natural conditions in a laboratory has become remarkably sophisticated. Today, laboratories can produce synthetic rubies, sapphires, emeralds, and diamonds that are chemically, physically, and optically identical to stones that took millions of years to form underground.

While these synthetic stones offer an affordable, ethical alternative to mined gems, they present a significant challenge for collectors, jewelers, and lapidary artists: how do you tell the difference?

Because a synthetic ruby is made of the exact same aluminum oxide (corundum) as a natural ruby, traditional tests for hardness or refractive index will yield the exact same results. The secret to distinguishing them lies not in what the stone is made of, but rather in the microscopic "birthmarks" left behind during its formation.

1. The Power of Inclusions

The primary method for separating natural and synthetic gemstones is microscopic examination of their inclusions—the internal characteristics, flaws, and trapped foreign materials inside the crystal.

Natural Inclusions

When a gemstone grows in the Earth, it does so in a chaotic, messy environment. As the crystal lattice forms over thousands of years, it traps bits of surrounding minerals, liquids, and gases.

  • Silk: Fine, intersecting needles of rutile (commonly seen in natural sapphires and rubies).
  • Two-Phase Inclusions: Cavities containing both a liquid and a gas bubble.
  • Included Crystals: Tiny, fully formed crystals of other minerals (like a small garnet trapped inside a diamond).
  • Zoning: Uneven, angular bands of color caused by changing chemical conditions during the stone's long growth period.

Synthetic Inclusions

Laboratory-grown gems form much faster and in highly controlled environments. As a result, they are often "too perfect." When they do have inclusions, they reflect the manufacturing process rather than a geological one.

  • Curved Striae: Flame-fusion synthetics (the oldest and cheapest method) grow in a teardrop shape called a boule. As the melted chemicals drip and cool, they leave microscopic curved growth lines. Natural stones never have curved growth lines; natural color zoning is always angular and straight.
  • Gas Bubbles: Flame-fusion and glass imitations often trap perfectly round gas bubbles. Natural gas bubbles are almost always trapped alongside a liquid in an angular cavity.
  • Flux Inclusions: Stones grown using the flux-melt method (often used for synthetic emeralds) may contain wispy, veil-like inclusions of the un-melted chemical flux, which look distinctly different from natural fingerprints.

2. Advanced Gemological Tools

While a standard 10x jeweler's loupe is a great start, conclusive identification often requires specialized equipment.

The Microscope

A gemological microscope with darkfield illumination is the most critical tool. Darkfield lighting illuminates the stone from the sides against a black background, making microscopic inclusions and curved striae stand out in bright contrast.

Ultraviolet (UV) Light

Many synthetic stones react differently to ultraviolet light than their natural counterparts. Because natural stones often contain trace amounts of iron (which dampens fluorescence), they may not glow under UV light. Synthetic stones, grown in highly pure iron-free environments, often exhibit intense fluorescence. For example, synthetic flame-fusion rubies usually glow a blinding, unnatural red under long-wave UV light compared to the softer glow of natural rubies.

The Spectroscope

A spectroscope analyzes the specific wavelengths of light absorbed by a gemstone. Because synthetics are colored using highly specific, pure coloring agents (like cobalt in synthetic blue spinel), their absorption spectrum will show sharp, distinct bands that differ from the messy, complex absorption spectrum of a naturally colored stone.

3. The Value of Disclosure

It is important to remember that there is absolutely nothing wrong with buying, cutting, or wearing synthetic gemstones. They possess the exact same durability and beauty as natural stones. The ethical breach only occurs when a synthetic stone is misrepresented and sold at the price of a natural, earth-mined gem.

For lapidary artists, cutting synthetic material (like synthetic sapphire or cubic zirconia) is an excellent, cost-effective way to practice complex faceting designs before risking an expensive piece of natural rough. By understanding the microscopic differences, you can navigate the gem market with confidence and transparency.