Inclusions: Are they friend or foe?

by carly_midgley | November 3, 2017 8:58 am

By Lauriane Lognay

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Gemstones are more than simply part of the piece
of jewellery they’re set in. Each stone has an origin,
and with it an amazing story to tell.

What are inclusions?

Inclusions are present in almost every gemstone and take many shapes and forms.

There are three types:  liquid, gas, and solid. Each forms at different times during the process of crystallization. They can be combined to form one, two, or three-phase inclusions. Liquid with gas, for example, would be a two-phase inclusion.

Inclusions are also the key to understanding the origin of a gemstone. They are the most important aspect in determining not only the formation of the gems, but also if it is natural or treated.

Why is the origin of a gemstone so important?

Proof of origin can be very important for pricing a gemstone. If you have a high-quality emerald and you don’t know how to determine the price, laboratories such as the Gemological Institute of America (GIA) or American Gemological Laboratories (AGL) will determine it by its origin. With emeralds, Colombia is the best origin. Zambia is also a good origin, however, their stones are not as valuable.

Paraiba tourmalines wouldn’t be Paraiba if it didn’t come from this location. It would be called cuprian tourmaline and wouldn’t have the same value.

According to the GemGuide, an independent pricing magazine for coloured gemstones and diamonds, if you have a one-carat good quality cuprian tourmaline from Paraiba, you could easily sell it for US$7000 per carat or more. However, if the same quality and size tourmaline is cuprian but not from Paraiba, the stone’s value decreases to US$2500 per carat.

Why are inclusions good for you and you client?

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Many jewellers will have a client that’s said they don’t want a gemstone because it has inclusions and believe them to be a sign of ‘bad quality.’

While some inclusions are a sign of bad quality, most of the time it’s good to have a few, even if they’re too small to the naked eye.

It’s possible to determine the origin of the gemstone by its inclusions most of the time by analyzing a stone’s chemical composition and formation of the inclusion within the gem. For instance, horsetail inclusions in demantoid garnet are Russian, as we know this has always been the only place one could find this specific inclusion.

In order to gain a client’s trust, inclusions should be shown to them in a loupe or through a microscope. In doing so, should repairs or changes need to be made to the piece of jewellery, the client will be able to recognize the gems as their own. This protects you, as a jeweller, from incidents when a client says it’s not their stone.

Added value

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As mentioned, some inclusions are wanted in gems, sometimes even pursued, because they improve the price and quality. For instance, quartz with rutile inclusions (normally, rutile inclusions are long needle-like and golden), are much more valuable than simple, colourless quartz. Like golden rutile, black tourmaline and red hematite inclusions give colour and life to a stone, and an even better price.

A green demantoid garnet from Russia with a perfect horsetail inclusion is desirable because of its beauty and the rarity of such a formation—the most beautiful specimens have a horsetail right in the middle of the stone, symmetrical, with long and flowing golden threads going through it.

From a perfect small spinel octahedron, to hundreds of needle inclusions parallel to each other in a sapphire that create an asterism or star sapphire, it’s possible to find rare, unique perfect crystal formations in gemstones.

Risky business

Gemstone setters know how a well-placed fissure can be risky business. Some smaller ones are usually no problem, but they are a less desirable trait found in a gem. If the fissure is not easily visible in the gem because it was oiled (most emeralds on the market are oiled to hide some flaws), it can be detrimental to the structure of the stone.

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Diagnostic inclusions

Some inclusions don’t play a role in the valuation process nor the structural integrity of the stone, but are practical in discovering its identity and/or if it’s natural or not. For example, a centipede inclusion in a moonstone is considered a ‘diagnostic inclusions,’ as it proves the stone, without a doubt, is moonstone. Other diagnostic inclusions would be an orderly pattern of small octahedral crystals for spinels, or what is called a ‘lily pad’ inclusion in a peridot—it is a chromite crystal with a decrepitating halo around it.

These are all natural inclusions found in gemstones. There are also inclusions found in synthetic gems and imitation gems like glass or plastic.

Natural vs. synthetic

Small crystals, fissures, and liquid inclusions generally indicate whether a gemstone is natural. They may not, however, be able to identify, whether it was treated or not. There are always exceptions to this rule, and that’s why laboratories exist to help. Labs can identify if material synthetic e.g. if the stone is glass, it will have swirls.

Each synthetic method has its own inclusions to recognize and identify.

The well-known synthetic method/process, ‘flame fusion,’ is often used to make rubies, sapphires, and spinels. These stones can be identified by white crystals, elongated bubbles, bubble clouds, and curved striae layers amongst other inclusions.

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Another well-known synthetic method is the hydrothermal process. It’s used to create emeralds, quartz, opals, rubies, and sapphires. The inclusions often include bread crumbs for quartz, and white veils, nail heads—a two-phase inclusion resembling nails—and a houndstooth pattern for emeralds.

Synthetics are harder to recognize as most of the time they don’t have any inclusions, which is why a gemstone with some natural inclusions is a good thing. The client can be sure he or she bought something natural. The only other way to be sure would be to go to a reputable gemmologist and have it checked.

One could say inclusions can be a jeweller’s best friend. They are important for determining value, durability, and the identity of the gemstone. Ultimately, it’s important for clients who are hesitant to buy gems with inclusion because they fear for the quality to know a stone with a few inclusions is always better than a gem without and no certificate of authenticity.

GENERAL INFORMATION ABOUT INCLUSIONS

There are three types of inclusion formation. Protogenetic: Inclusions formed before the crystal host. Pyrite inclusions in emerald would be a perfect example. The pyrite was formed before the emerald crystal was ever created. Syngenetic: Inclusions formed at the same time as the host crystal. These are most of the gas or liquid inclusions seen in gemstones. For example, liquid inclusions in tourmaline, also called hair inclusions, or more scientifically, trichites, are syngenetic. Epigenetic: Inclusions appearing after the formation of the crystal host. Tension fissures in any gemstone or laser-drilled holes in diamonds, also considered a treatment, are epigenetic.

Lauriane Lognay is a fellow of the Gemmological Association of Great Britain (FGA), and has won several awards. Today, she is a gemstone dealer working with jewellers to help them best decide the stones for their designs. She is the owner of Rippana Inc., a Montréal-based company working internationally in coloured gemstones, lapidary, and jewellery services. Contact Lognay via e-mail at rippanaininfo@gmail.com

Source URL: https://www.jewellerybusiness.com/features/inclusions-friend-foe/

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