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Gemspedia >> Gems >> Synthetic & Simulants

Synthetic & Simulants

The desirability and high value of gemstones has long meant that some gems are unobtainable for many people. Filling the gap for their demand, are the almost identical looking but inexpensive substitutes, created and simulated gems.


While occasionally used to deceive even the most experienced eyes, most created and simulated gems are honestly used in a wide range of applications ranging from fashion jewelry to radio components and watch bearings.

 

The gem trade draws slight distinctions between created and simulated gems based on whether they have exactly the same properties of the material they are trying to imitate.

 

Created gemstones

Created Gemstones are identical to their natural counterpart in every way (i.e. hardness, composition, optical properties etc.); the only difference is that they are created in a laboratory not in nature. For example, created sapphires are made of corundum, the same base mineral as natural sapphires, and have essentially the same optical, physical, and chemical properties as natural sapphires.

 

Created gemstones are also known as “laboratory grown”, “laboratory created”, “[manufacturer name] created” or “synthetic” gemstones. Technically, no created gemstone is rare, as they can be made anytime.

 

A variety of methods are currently used in the production of created crystals, resulting in different qualities, appearances and prices.

 

The flame fusion or Verneuil process

Trapped gas bubbles are clearly visible in this synthetic flame fusion blue sapphire. Trapped during synthesis, such bubbles are not seen in natural ruby and sapphire.

This was the first process used for gemstone synthesis and is still extremely common. With low production costs and high crystal growth rates, large numbers of flame fusion gemstones are readily available. It is the most inexpensive crystal production method and offers very good value for money. Consequently, it is also used to make the majority of created rubies, sapphires and spinels.

 

The method utilizes the powdered ingredients of a gem by fusing them together under a high temperature oxy-hydrogen flame. The ingredient powder melts and crystallizes in successive layers. This method fortunately leaves us a wealth of clues regarding its manmade origin. Important identification features are curved growth layers resulting from crystallization in layers. These are best observed under a 10x loupe or microscopic. Often present too, though slightly harder to see, are clouds of gas bubbles.

 

Flux-melt technique

Flux remnants in a flux-grown synthetic ruby.

This is a high quality gemstone synthesis technique rarely used in fashion jewelry or industrial applications due to higher production costs. These synthetics pose the greatest threat to the gem trade as flux grown rubies have inclusion patterns that very closely mimic natural fingerprint patterns seen in natural rubies.

 

Molten fluids or fluxes are used to manufacture flux-grown gemstones. By dissolving gem-producing ingredients in the fluid and then crystallizing them under controlled conditions to produce the desired gem mineral.

 

While the physical properties of natural and flux-grown gems are the same, the clues to their synthetic origins are usually found on the microscopic level. Small, often hexagonal platelets from the side of the platinum crucible are proof of synthetic origin. Also seen are flux fingerprints that have solidified residues within the fingerprint cavities.

 

The hydrothermal technique

Commonly used in manufacturing high quality synthetic emeralds, this process closely mimics how many crystals in nature originate from high temperature, high pressure water solutions.

 

The ingredient materials are enclosed in a partially filled, sealed container of water. Heated to high temperatures the feed materials are dissolved and at point of cooling crystal growth is induced.

 

Imitation gemstones

Also known as simulants, imitation gems don’t have the same properties (i.e. optical, physical, and chemical etc.) as natural gemstones but resemble the natural gemstone they imitate. A simulated gemstone can be any material that takes on the appearance of a natural gemstone. Even obvious imitations such as glass or plastic can be accurately described as simulated gemstones.

 

However, please be aware that a created gemstone can be described as either a created gemstone or a simulated gemstone depending on how the material is marketed. For example, violet sapphire can be created in a laboratory and called “synthetic violet sapphire” or used to simulate violet quartz and called “imitation amethyst.” Similarly, color change sapphire can be created in a laboratory and called “synthetic color change sapphire” or used to simulate color change chrysoberyl and called “imitation alexandrite.”

 

Another example of a simulated gemstone is synthetic cubic zirconia (CZ), marketed as a diamond imitation under a variety of brands names. Synthetic cubic zirconia resembles diamond but does not have the same properties as diamond. While a number of diamond simulants exist, only synthetic cubic zirconia and synthetic moissanite have commercial significance.

 

Synthetic cubic zirconia

Produced by the skull-melt process, synthetic cubic zirconia is an inexpensive diamond simulant and an excellent alternative to diamond. Although mostly seen in its white or colorless forms, CZ (as it is commonly known) is also available in a wide variety of colors. Nearly as hard as ruby and sapphire, the optical properties are high and CZ has good brilliance. Despite its near stranglehold on the diamond simulant market for the last two decades, the introduction of synthetic moissanite has provided some competition.

 

Synthetic moissanite

Synthetic moissanite is a very hard and brilliant jewel manufactured by man. Found naturally in asteroids and meteorites, scientists only started manufacturing moissanite as gem simulant fairly recently.

 

Showing even more fire than a diamond, moissanite has a hardness of 9.25, which makes it harder than any gem except diamond. While considerably less expensive than diamonds, it is expensive in comparison to other man-made gem materials.

 

Moissanite is a synthetic that provides the gem trade with the best of both worlds. To the naked eye, moissanite is virtually indistinguishable from diamond. Under a 10x loupe it is quite easy to distinguish from diamond due to its heavy double refraction, manifesting as the doubling of facet edges.

 

The following table compares the properties of diamond with synthetic cubic zirconia and synthetic moissanite:

 

Diamond

Syn. Cubic Zirconia

Syn. Moissanite

Composition

Native carbon

Zirconium oxide

Siicon carbide

Crystallography

Cubic

Cubic

Hexagonal

Refractive Index

2.417

2.15 to 2.18

2.65–2.69 (0.040)

Specific Gravity

3.52

5.40 to 5.95

3.22

Hardness (Mohs)

10

8.5

9.25

Dispersion (B–G)

0.044

0.058 to 0.066

0.104

Composite gems (assembled stones)

The separation plane of a ruby doublet is visible at the girdle. This doublet consists of a natural green sapphire crown on top of a synthetic ruby pavilion.

Known as doublets or triplets, these gemstones consist of two or more parts that have been artificially joined together to give the impression of a single gemstone.

 

The component pieces of composite gemstones include combinations of natural, created or simulant material. Color usually derives from one component only or sometimes from dyes within the layers.

 

Composite gemstones are most realistic if natural gem material is used for the crown of a faceted gem, as casual inspection reveals natural inclusions. Pictured here is a ruby doublet with a natural sapphire crown joined to a synthetic ruby base, giving the appearance of a large ruby with natural inclusions. Clearly visible is the junction where the two parts meet.

 

Popular doublets include ruby doublets, sapphire doublets and alexandrite doublets. These should not to be confused with the doublets seen in amber, opal and ammonite as these are constructed only to provide an otherwise fragile


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