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Lab Grown Gemstones & Synthetics 101

There’s a lot of debate around natural gemstones versus lab grown gems. Today, we want to go over the key differences between the two types of stones and shed some light on the history of synthetics and the modern techniques used to produce lab grown gemstones. Let’s pull back the curtain.

What Are Lab Grown Gemstones?

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What are lab grown gemstones? This term is used very specifically in gemology. It’s not a simulant, which is an imitator of a different gemstone. It’s not a fake gemstone. Lab grown gemstone is the artificial counterpart to a real, naturally occurring mineral.

Lab Grown Gemstones vs Natural

So, what’s the real difference between a natural and a lab grown gemstone? A natural gem is exactly how it sounds: formed entirely by nature and without human intervention or modification, aside maybe from polishing or fastening.

Are lab grown gemstones realThe lab grown gemstone has the exact same chemical, physical, and structural properties as its natural form. Some gemstones are more difficult to synthesize than others, and not all stones are commercially viable to attempt to synthesize.

What Gemstones Can Be Lab Grown?

The most common lab grown gemstones seen on the market today are Ruby, Sapphire, Emerald, and Spinel, with diamonds to a lesser extent but of equal importance.

How Are Lab Grown Gemstones Made?

Now, let’s take a look at how lab grown gemstones are made. For Ruby and Sapphire, the process is the same since they’re the same variety of gemstone: corundum.

You take your base corundum ingredients – aluminum oxide powder, which produces synthetic white sapphire – and add coloring agents to get the red or blue you desire.

What Processes Are Used To Make Lab Grown Gemstones?

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Vernoy Flame Fusion Process

The primary method for synthesizing Ruby and Sapphire is called the Vernoy Flame Fusion process, named after the man who first synthesized Ruby in 1902. It was the first commercial process used, and it’s still very important today due to its low production cost and high growth rate. Other lab grown gemstones made with this process are spinel, rutile, and strontium Titanite.

So, you take your powder of the right components to create whichever stone you’re going for, and pass it down through an extremely hot oxyhydrogen flame, which for corundum needs about 2,000 degrees Celsius or over 3,600 Fahrenheit. This melts the ingredients, which drop onto a plate and solidifies into a single crystal called a bool. This process takes a few hours and yields a crystal with the same refractive index and specific gravity as the natural version.

Flux Melt Growth Process

The vernoy flame fusion process has yet to work for emeralds, so different methods to synthesize it are used, including one called flux melt growth, which is also used to make synthetic Alexandrite.

Emerald was the first stone synthesized with the flux melt growth process in a heat-tolerant crucible like graphite or platinum. The gem ingredients are dissolved in a molten fluid or flux, where it recrystallizes to form the desired gem material.

Using this method, crystals can take two months or up to a year to grow, depending on the size you want. This makes it more costly than the vernoy method, but corundum can also be synthesized in this way.

One thing to look for in a flux melt Emerald is tiny platelet inclusions from the crucible itself. You can also find veils of feather-like inclusions, and sometimes small cavities filled with flux will also occur.

Hydrothermal Growth

Another synthesizing technique is hydrothermal growth, which attempts to imitate the natural process that creates many natural gemstones.

Mineral-rich water under high heat and pressure can cause gems to crystallize over time. So to replicate that, the required gem materials are sealed in a container of water, and it’s essentially pressure-cooked. Steam can’t escape, and the water is heated beyond its boiling point. This allows materials that are normally insoluble to be dissolved.

Quartz can also be made in this way. Emerald requires temperatures of 600 Celsius and 1,000 times atmospheric pressure and grows about a third of a millimeter a day for two weeks. Since the container is under tremendous pressure and sealed up, you can’t add more material to it during the process. If you want a larger stone, you can start with a seed gem from a previous batch, and the new material will crystallize on it.

The traits of hydrothermal emeralds are similar to flux melt emeralds. There can be wispy veil inclusions and metal inclusions from the container. Both also appear bright red under a Chelsea filter, but so do some Colombian emeralds, so this test needs to be more conclusive.

Can You Tell If A Gemstone Is Lab Created?

You may be thinking that even though the ingredients are the same as a natural stone, it’s forming in a different way than a natural stone and in a much shorter time. Surely this will yield some differences, right? It does, but they’re subtle.

Air Bubbles

You need at least a 10x loop to detect most of these differences.

For one, air bubbles could have gotten trapped inside the bool during the formation process. This tends to be seen more in older vernoy synthetics and is mostly absent in modern synthetics. These bubbles are very small and, without stronger magnification, can appear as tiny dots rather than obvious pockets. But they still stand out because of the difference in RI between the gas and the crystal.

Parallel Curved Lines

Secondly, in a gemstone cut from a bool, you may see parallel curved lines or color bands resulting from the formation of the bool. These can only be seen from certain angles, though; in lighter-colored stones like a yellow Sapphire, for example, they may be nearly impossible to spot. You can also get chatter marks, which are a fire-like or a crack-like pattern seen on the surface of a faceted synthetic stone that has been polished with insufficient care.

All synthetic spinel is made with this same vernoy process, but the distinguishing features are different than those of corundum. The chemical and physical properties of synthetic spinel are slightly different from natural spinel, but it’s still considered synthetic. The refractive index of a natural spinel is 1.718, whereas the RI of a synthetic spinel is about 1.727.

Too much aluminum oxide in a spinel induces stress in the crystal structure of the stone, which can be seen as hazy patchiness using a polarized lens. Gas bubbles are also possible in synthetic spinel, but they tend to be more complex in shape than corundum bubbles.

how are lab grown diamonds made?

lab-grown gemstones

Lastly, let’s talk about lab-grown diamonds. The first ones created in 1953 were small and used for industrial purposes. Gem-quality crystals would only be produced for a few years. There are three different utilizations of HPHT or high-pressure high-temperature synthesization: the belt press, the cubic press, and the bars method, which claims to be the most compact and economical, though all have their advantages, and they all generate ridiculous heat and pressure.

Another newer method of diamond synthesis is chemical vapor deposition, or CVD, which uses hydrocarbon gas. It’s simpler and more flexible than HPHT, and it doesn’t require heat or pressure. To put it simply, a gas cocktail with some carbon source is pumped into a chamber where it crystallizes onto a waiting substrate that will allow the diamond to form with the right structure.”

The result is a wide, flat disc of a diamond – the world’s most expensive coaster. Usually, lab equipment is required to determine if a diamond is natural or lab-grown. Things to look for are color zoning, called hourglass or Maltese cross zoning. They also react more strongly to shortwave UV light than long-wave, which is the opposite reaction of natural diamonds.

You can also have little breadcrumb inclusions of dissolved metal and dust. These tiny metal inclusions can also cause lab-grown diamonds to be attracted by strong magnets. However, as lab-grown diamonds increase in quality, these inclusions appear less and less, sometimes indicative of an older diamond.

Conclusion On lab grown gemstones

The quality of lab grown gemstones is improving yearly, and they are very difficult to tell apart from their natural counterparts. Hopefully, today you learned something about synthetic versus natural stones. With all that said, are you team natural or team synthetic?

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