How to tell the difference between natural rubies, sapphires, emeralds from synthetics?
Lookswise there is no difference between synthetics and natural gemstones. They have the same chemical composition, crystal structure, and properties as natural gemstones. The only way to tell is by looking at internal inclusions or clarity characteristics. The price difference between natural gemstones vs synthetics are also significant. A 5 carat natural ruby, sapphire, emerald will cost over US$5,000. 5 carat synthetic gemstones will cost less than US$5.
True Story – Buying a Synthetic Instead of Natural Ruby
To start today’s blog post I want to tell you a true story. My friend who bought a ruby from Myanmar (Burma) when he visited there. This story can occur anywhere in the world. Especially, in countries where consumer protection is less stringent.
Tomchai was visiting Myanmar (Burma) with a tour group. He was enjoying his time as he didn’t have to stress in planning anything during the trip. Near the end of the tour, his tour guide took them to a ‘large’ retail jewelry shop. At the store, he saw some amazing gemstones and jewelry.
One thing which stood out for him was a 5 carat ruby. It looked amazing and the price was cheaper than similar ones you can get in Bangkok, Thailand. Also, he knew that Myanmar is famous for premium gemstones especially rubies. Tomchai thought why not get one ‘from the source.’
He asked a few questions and impressed with large store & inventory he saw. Thus, he was confident that the retailer he was dealing with was trustworthy. How can something go wrong if everything else in his trip worked out?
Got In-House Certificate
Tomchai decided to buy the ruby and received an in-house certificate from the shop. This made him even more confident that he made the right choice. He brought the ruby back to Bangkok to give it to me so I can set the stone in his new custom ring.
While giving it to me, he told me to check it and let him know my thoughts on the ruby. Using my office microscope I checked the stone. Almost immediately I saw curve striae. This is the fastest way to identify a flame fusion synthetic ruby.
Unfortunately, I had to convey to him the bad news. This made him pretty angry as he paid his hard-earned money on this synthetic ruby. The seller had not disclosed it.
Why is It Important To Tell Difference Between Synthetics (or Imitations) From Natural Gemstones
Separating natural gems from synthetics (or imitations) is definitely an important skill. We gemologists have to learn to tell difference as it is essential when buying or selling any gem. Without this basic knowledge, one can lose money and damage their reputations quickly.
Also, once one knows the gemstone is synthetic or treated, it is important to disclose it. Or else reputation and financial consequences can be severe. So, there is no excuse for lack of disclosure or lack of knowledge.
Synthetics vs Imitations Definition
In this post, I will summarize what we as gemologist check to see the difference between natural, synthetics or imitations.
First the definitions of synthetics and imitations are provided below:
Synthetics gems are made in a laboratory (or manmade). They have the same chemical composition, crystal structure, and properties as natural gemstones.
Imitation gems (also called stimulants) can be both natural and manmade. They only look like the gems they are replacing. While their chemical compositions and properties are completely different from gems they imitate.
Clarity characteristics are the best way to check synthetic gems. It shows the method by which they were manufactured. Below I will provide the most typical manufacturing methods.
Flame Fusion Synthetic
- Curved color banding or parallel curved lines called curved striae
- In contrast, natural gemstones have straight or angular growth patterns
- Gas Bubbles might also be presented
How to Detect
- Synthetic Rubies. Easy to detect curved striae in ‘red-color’ synthetic ruby through darkfield illumination setting
- Darkfield illumination is the normal setting in gem microscope or portable darkfield loupe.
- Synthetic ‘Blue’ Sapphires. Difficult to detect through normal darkfield illumination. Because Curved color banding is ‘blue’ in color. Using ‘diffused’ light can help.
- Create diffused lighting by placing a translucent filter between the stone and light. Translucent material includes white plastic, a sheet of paper or plain tissue
- Synthetic ‘Yellow or Orange’ Sapphires. Difficult to see through microscope as blub produces a strong yellow light. This overwhelms faint yellow or orange banding. A blue filter works best in this situation
- Blue filter includes clear blue transparent sheet or blue plastic
Flame fusion synthetics are the most common type of synthetics. They produce synthetic corundum (ruby or sapphire family) or spinel.
In flame fusion, powder chemicals are dropped through a high-temperature flame. As they melt they fall onto a rotating pedestal. Then are crystallize and form an elongated cylindrical synthetic crystal called a boule. This boule is eventually cut to make several individual synthetic gems.
Due to this process, it is easy to tell the difference between synthetic from natural gems. They have curved color banding or parallel curved lines, called curved striae. While natural gemstones have straight or angular growth patterns.
Flux Growth or Hydrothermal Synthetic
Flux Growth – Visual Characteristics
- Coarse looking fingerprint-like inclusions
- Coarse looking means white and high relief
- Natural gemstones have liquid droplet fingerprint inclusions. ‘Less’ coarse like than flux growth synthetics
- Wispy Veils
- Tiny droplets pattern called “rain”
- Parallel, uniform growth planes – sometimes called the “Venetian blind effect”
- Platinum crystals, often in the form of triangular or hexagonal platelets
- Colorless, low-relief phenakite or chrysoberyl crystals
Hydrothermal Growth – Visual Characteristics
- Fingerprints & veils
- Note: Extra time and care needs to be taken as they look similar to natural gemstones
- Chevorn-type growth zoning or wavy growth planes
- Phenakite or chrysoberyl crystals, gold rods and platelets
- White particles randomly scattered or forming ‘comet tails’ or stringers
- Seed plates in Biron material
- “Nailhead” or spicule inclusions
Flux growth and hydrothermal growth synthetics are solution based processes. They are generally slower and much more expensive compared to melt process synthetics.
Flux growth process. Powdered ingredients is combined with flux in highly heat-resistant container called a crucible. Then very high temperature is applied. So the flux melts and dissolves the powdered ingredients to form a chemical solution. As the solution cools the synthetic crystal formed.
Hydrothermal growth process. Heat and pressure applied to water, seed crystals and crushed chemical compounds. When chemicals dissolve they rise to the top. Then when the ingredients cool down, they start gathering around the seed crystals. This builds a large synthetic crystal.
Flux growth is usually used to produce more expensive synthetic corundum. The family name for rubies and sapphires.
Hydrothermal growth is a popular method for synthetic beryls. The family name for emeralds.
There are other processes that make other synthetics gemstones. But for this post I am focusing on only big three gemstones, rubies, sapphires & emeralds.
As defined earlier imitation gems are either natural or manmade. It takes the place (or imitate) a natural gem. ‘Variety of materials’ make imitation gems. The most common shown below:
Glass can imitate gems of all colors as well as colorless ones.
Very common to see it imitate all gemstones like:
e) Any other gemstone – transparent or opaque.
Surface appearance is often enough to separate glass imitation from gemstones. Gemstones are ‘high’ in the mohs scale (harder than glass). Glass facet edges are generally more round, and facets can sometimes be concave.
Glass jewel is also more commonly molded rather than cut. So its surface can have pitted and uneven with the ‘orange peel’ effect which is a result from the mold process.
Glass also feels ‘warm’ to touch because it doesn’t conduct heat as well as most crystalline gems
How to Detect Glass
Swirl marks are also common feature in glass which has a pattern linear flow structure. These patterns are actually layers of slightly different composition. Cause by ingredients that aren’t thoroughly mixed together. Swirl marks might look curved. But are coarser and less regular than synthetic curved striae.
Gas bubbles is also very common trait in glass. They contain large, round, randomly arranged bubbles. The bubbles are usually larger than flame-fusion synthetics. They also often aligned along the swirl marks.
If you have a polariscope then it is easy to distinguish glass with rubies, sapphires or emeralds. As these gemstones are double refractive while glass is single refractive. Sometimes under polariscope, a glass imitation often shows snake-like bands.
An imitation gem can also assemble together into two or more pieces of material. They are either fused or cemented together. Two pieces make it a doublet, three a triplet. The components are made with various materials. This can include natural, synthetic or imitation versions of gems.
Corundum – Doublets Most Common
For corundum, doublets are the most common. They usually made with a thin crown of natural sapphire at the top. With a flame-fusion synthetic ruby or synthetic sapphire base at the bottom.
You can identify them by looking for the separation plane. And color difference between the layers. They also typically have natural inclusions in the crown. And flame-fusion type inclusions in the base.
Some assembled triplets imitate emeralds. With actual natural gem materials at top and bottom. And colored glass or some material providing the imitation’s green hue.
For emerald imitation usually, a layer of green cement is between a crown and pavilion of pale beryl. The natural portions have beryl’s refractive index (RI) and birefringence. It might also contain natural inclusions.
Best way to detect assembled stones is by looking at them from the side. Which you can usually see the place where the crown and pavilion joined together. Most assembled stones are mounted in bezel settings to hide their separations planes.
Plastic is versatile material that can imitate many gem materials. They are transparent, translucent, organic or phenomenal.
Plastic’s luster is like the luster of many organic gems, so it’s used most often to imitate them. But it is not very durable and it melts during any repair work and it is very soft so it scratches easily.
Under magnification, gas bubbles in plastic appear in a variety of shapes.
Like glass, plastic jewelry usually also has:
a) Concave facets
b) Rounded facet junctions
c) Orange-peel effect
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