Diamonds. Rubies. Sapphires. Emeralds. These stunning gemstones are known for their brilliance, beauty and dazzle, accounting for some of the world’s most stunning jewelry. But there’s more to these gemstones than meets the eye. While some gemstones are technically “flawless,” most have at least some trace imperfections. These imperfections, known as inclusions, are fascinating and can even help identify gemstones. Learn more about gemstone inclusions and what to look for as you pursue purchasing a gem of your own.
What are gem inclusions?
An inclusion is any material trapped inside a gem’s structure during formation. These tiny imperfections can be composed of various substances such as other minerals, gas bubbles or even liquid.
An inclusion's specific composition and appearance can offer valuable clues about the gemstone's formation process. Think of them as a gemstone's fingerprints, providing clues to its origin and history. While some inclusions can affect a gem's clarity, others are unique and can even add to its value.
Types of inclusions
Inclusions come in different sizes, made from different materials. While many inclusions are made up of the aforementioned foreign materials present during the gem's formation, some inclusions result from cracks or fractures that cause visible imperfections. Here are a handful of common types of gem inclusions:
Solid inclusions
These inclusions are tiny crystals, minerals or even other gemstones—like quartz — trapped within the gemstone. They are formed as the gemstone grows and incorporates these foreign materials. Some common solid inclusions are calcite crystals in emeralds, zircon in sapphires or garnet in diamonds.
Fluid inclusions
As the name suggests, these are tiny bubbles of liquid trapped inside the gemstone. Although fluid inclusions are typically quite small (usually less than 20 micrometers, or one-fifth the width of a human hair), their physical and chemical composition are easy to determine and can provide useful data to estimate the temperature and pressure at the time of the gem's formation.
Gas inclusions
Like fluid inclusions, these are bubbles of gas such as carbon dioxide or nitrogen trapped within the gemstone. Gas inclusions typically appear spherical and elongated. If a gas inclusion within a gemstone appears perfectly round, it may indicate it was lab-grown. While gas inclusions are commonly found in natural glass gemstones like obsidian, they are rarer in other gems.
Feather inclusions
While actual feathers can (very rarely!) be found within gemstones, feather inclusions refer to tiny fractures, cracks or breaks within a gemstone. Caused by stress or damage during formation, feather inclusions can have a negative impact on a stone’s durability. Some feather inclusions can be spotted by someone with a keen naked eye. However, they are often quite small and only occasionally impact a gemstone’s overall appearance.
Needle inclusions
These long, thin, needle-like inclusions are often made of rutile, a titanium dioxide mineral. Needle inclusions often cause the optical phenomenon called asterism, forcing light to reflect in a particular way, creating a star-shaped pattern. These rutile needle inclusions create popular, unique gems such as star sapphires and star rubies.
Inclusion phases
Gem inclusions are classified based on the number of phases (solid, liquid or gas) present. Some gems have no inclusions, while others contain all three phases.
Single-phase inclusions
These inclusions contain only one phase, usually a solid, such as a mineral crystal or trace amounts of another element.
Two-phase inclusions
These inclusions contain two phases, typically a liquid and a gas bubble. They often have a mobile gas bubble that can be seen moving within the liquid when the gemstone is tilted.
Three-phase inclusions
These inclusions contain all three phases: solid, liquid and gas. The solid phase is usually a tiny crystal suspended within the liquid where a gas bubble is also present. Three-phase inclusions are particularly common in emeralds.
History of gem inclusions
While the existence of gem inclusions has been known since ancient times, their significance and impact on gemstones were not fully understood until the 19th century. Renowned mineralogist Gustav Rose developed an understanding of gem inclusions through his detailed descriptions and classifications of minerals, including those found as inclusions in gemstones. His work helped establish a framework for identifying and understanding these internal characteristics.
Advancements in technology, especially the development of microscopes, spectroscopy (the study of the absorption and emission of light and other radiation by matter), and the use of ultraviolet light examination have allowed for more detailed analysis. Sophisticated instruments like Raman spectroscopy and infrared spectroscopy provide unprecedented insights into the composition and formation of inclusions. This knowledge has transformed gemology, allowing experts to identify the origin of gemstones and potentially detect treatments accurately. Laser technology has allowed for the removal of some surface-level imperfections; however, deep-seated inclusions are incredibly difficult to target without damaging the gemstone. Furthermore, the process can alter the gemstone's optical properties, diminishing its value and beauty. Any attempt to remove inclusions carries a high risk of irreparably damaging the stone.
FAQs: Frequently asked questions about gemstone inclusions
- How can you see inclusions? Inclusions are typically microscopic and require magnification to see. Gemologists use loupes and microscopes to examine gemstones for these tiny imperfections. Some larger inclusions may be visible to the naked eye, especially in larger stones.
- Do inclusions affect the value? The impact of inclusions on a gemstone's value depends on several factors, including the type, size and location of the inclusion. While some inclusions can detract from a stone's clarity, others can enhance its beauty.
- For better: The word “imperfections” may give inclusions a bad reputation. However, some gemstones, like the star sapphires mentioned above, contain such mesmerizing effects from inclusions that they’ve become highly sought after by collectors and consumers alike, commanding a premium price.
- For worse: An inclusion in the crown (top) portion of a diamond can obstruct the light, reducing the diamond's brilliance and fire. This diminished sparkle directly impacts its perceived quality and, consequently, its price.
- How common or rare are inclusions? Inclusions are incredibly common in gemstones. It is rarer (extremely!) to find a gemstone with no inclusions. Despite being very common, the specific types of inclusions and their abundance vary greatly from gemstone to gemstone.
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