Natural gemstones have remained an enigma for thousands of years, but only in mankind’s recent history have we uncovered the gemological science behind the processes that form them. Gemstones are formed due to the cooling of molten rock and magma within the Earth’s crust. The cooling causes the molten rock and magma to condense and release minerals, which then grow into crystals. If sufficient space is available, these crystals grow into larger, more structured arrangements that we call gemstones.
Since gemstones are formed in different environments and conditions within the surface of the Earth, certain liquids, gases, or solids often get trapped inside the growing crystals and forever become a part of them - resulting in what are known as inclusions. While some may consider inclusions a blemish in the clarity of a gemstone, others see them as intricate designs that enhance a gemstone’s beauty with their unique fingerprint. But which gemstone inclusions should you avoid, and which ones should you seek? What do gemologists say about inclusions and the origin of a gemstone, and how can they affect its value? Keep reading to find out.
What Are Inclusions?
Foreign materials that get trapped in a gemstone’s crystals during its gemological formation, are called inclusions. They can be either microscopic (requiring magnification) or large enough to be seen by the naked eye. They can also occur individually or in small clusters and can be sizable enough to affect the clarity of the gemstone. Inclusions are usually present randomly throughout the gemstone, but can also form along certain crystallographic directions, colour zones, and healed fractures. They can also occur in geometric patterns related to the gemstone’s crystals.
Solid inclusions can exhibit their own shape and structure - having a rounded or irregular appearance, while fluid inclusions usually have a geometric shape that may reflect the typical crystal form of the host. For this reason, fluid inclusions are often referred to as “negative crystals” by expert gemologists. Sometimes gemstones can have both solid and liquid inclusions, for example, topaz. Gas inclusions are usually present in rounded or irregular shapes.
How Are Inclusions Classified?
Inclusions can be classified based on their state - solid, liquid, or gaseous, and based on their abundance and frequency. Inclusions can be singular or multi-state and can occur in combinations of these different states of matter. Multi-phase inclusions, which are inclusions containing two or more immiscible liquids, are formed when a compound mixture gets trapped within the gemstone under high temperature and pressure and separates as the gemstone cools down.
How Frequent Are Inclusions in Gemstones?
Most natural gemstones mined from the surface of the Earth contain some form or type of inclusions. In fact, inclusions are so common in gemstones that they are the very first test in determining whether a gemstone is natural or lab-made. The majority of natural gemstones available today contain inclusions and are almost always treated to enhance their clarity. Encountering a perfectly clear and untreated natural gemstone is extremely rare, and such specimens usually cost a fortune. Read more about the treatment of inclusions here.
Common Types of Inclusions
The inclusions present in a gemstone can indicate its mine of origin, as well as its history, and geological formation process. Specific inclusions can be studied and examined to differentiate the region the gemstone has been sourced from, and gemologists often categorise inclusions based on their appearance (shape, size, transparency, colour, lustre, orientation, etc.). The following is a non-exhaustive list of some typical inclusions found in a majority of natural gemstones available today.
1. Mineral Needles
Minerals like rutile often appear as inclusions in corundum stones. These can be present in the form of fine needles and can enhance a gemstone’s appearance through effects like chatoyancy, asterism, and silk.
- Chatoyancy/Cat’s Eye Effect: This is observed when a gemstone contains homogeneously distributed parallel rutile needles throughout its volume. Light can reflect from these inclusions and create a luminous band that resembles the eye of a cat - giving rise to the name “cat’s eye stones”. The “cat’s-eye effect” is the most distinct and sharp in chrysoberyl gemstones. Their characteristic appearance adds a distinct flair to jewellery pieces.
Figure 1: A Chrysoberyl Cat's Eye Stone with a sharp chatoyance (Source: The Gemmological Association of Great Britain)
- Asterism: This is a phenomenon in which needle bands are oriented in different directions within the gemstones. It produces the appearance of star-shaped bands in gemstones and gives rise to unique-looking gemstones like star rubies and star sapphires. These needle inclusions that produce star-shaped bands are also common in garnets. These gemstones, with their distinctive appearance, are usually cut into polished and rounded shapes called cabochons, instead of being cut into faceted gemstones.
Figure 2: The Rosser Reeves Star Ruby (Source: The Natural Ruby Company)
- Silk: Short and fine needles may occur in zones or clouds. These are referred to as “silk” in the gemstone trade and are commonly found in coloured corundum minerals from Ceylon (now, Sri Lanka) and Burma (now, Myanmar). These intricate inclusions scatter light within the gemstone - creating a soft sparkle, and when combined with the slight fluorescence of a gemstone, enhance its brilliance. This is a contributing factor to the popularity of Burmese rubies as well as blue and yellow sapphires from Ceylon - making them the most sought-after variety of sapphires in the trade.
Figure 3: "Silk" rutiles in a Neelam Stone (Source: GIA)
- Pargasite Needles: These are another type of mineral inclusions, characterised by long fine needles, fine dust clouds and crossing dust tracks, akin to the strokes of a brush. These can be found in Neelam stones from Kashmir, Sri Lanka, and Madagascar. Upon a closer examination of the patterns, subtle differences can be revealed to identify the gemstone's mine of origin.
Figure 4: Pargasite needles in a Kashmir Blue Sapphire (Source: GIA)
2. Colour Zoning
The trace elements present within a gemstone’s crystals, such as chromium in rubies or titanium in corundum minerals, are responsible for the production of colour in a gemstone. These elements are usually present in uniformity throughout the gemstone, but physical and chemical changes over thousands of years can change their concentration and lead to variations in the gemstone’s colour.
The usually imperceptible variations can, at times, be quite distinct. There can be a diversity in the colour or the concentration of defects, and these can occur in coloured bands or zones. This phenomenon is called colour zoning. And because gemstone crystals grow in different directions, different growth planes can have varying chemical compositions and form colour zones and bands in multiple orientations. Colour zoning does not affect the gemstone’s structural integrity and can make for jewelry pieces that stand out. Watermelon tourmaline is one such gemstone that displays a unique band of colours. It is a rare variety of tourmaline characterised by a red or pink centre and green exterior–similar to that of its namesake fruit.
Figure 5: Sharp colour zoning in an Emerald when viewed from the bottom (left) as against the top (right) (Source: GIA)
3. Fractures & Fissures
Fractures and fissures are common in gemstones and play a big role in determining clarity. They can be present in different shapes and sizes, and large fractures or cavities can be dangerous for the structural integrity of a gemstone. Fractures and fissures can also cause inclusions like feathers and fingerprints..
- Feathers: Feathers are small cracks or breaks in the gemstone. They usually have a whitish or translucent appearance but can be darker as well. In most cases, feathers are harmless but sometimes, they may compromise a gemstone’s strength, especially if the feather reaches the surface. As such, these should be checked by an expert before purchase.
Figure 6: Feather in a natural sapphire (Source: The Natural Gemstone Company)
- Fingerprints: Sometimes fractures that form while the crystals are still growing can heal themselves and give rise to beautiful tube-like patterns within the gemstones. These tube-like patterns are called fingerprints.
Figure 7: Fingerprint inclusion in a sapphire (Source: Pinterest)
Several processes can be used to treat gemstone fractures and enhance their clarity and transparency. Different thermal enhancements are done to rubies, sapphires, and diamonds to enhance their colours and melt certain types of inclusions. The use of artificial resins and oils is common in beryl minerals, especially emeralds. Read more about the treatment of fractures and fissures here.
How Do Inclusions Impact a Gemstone’s Value?
The value of a gemstone is determined by the 4Cs: Carat weight, Cut, Colour, and Clarity. Clarity is an important aspect of a gemstone and is often affected by inclusions. Some gemstone inclusions, like silk, may enhance the beauty of a gemstone by making it more scintillating and brilliant when used in jewelry. Others can cause a loss of clarity and make it appear speckled. That being said, clarity, and all other aspects, are a matter of personal preference - some may prioritise the colour saturation of a stone, while others may place more importance on clarity. It's worth noting that, as long as an inclusion does not affect a gemstone's structural integrity, there is no reason not to purchase it.
As we said earlier, gemstone inclusions can give deep insights into the origin and history of a gemstone. Rubies from the deposits in Mogok Valley, Myanmar, for example, may have calcite inclusions, while spinels from the same region in Mogok may have dolomite inclusions. Similarly, emeralds from Russian mines may contain mica inclusions while emeralds from the Muzo mines in Colombia, where the gems are found in veins with carbonate, quartz crystals, and pyrite, may have inclusions of carbonate minerals. This way, gemstone inclusions can help indicate the rarity or relative abundance of a certain gemstone, and thereby determine its origin and value.
Figure 8: Mica inclusions in a rough Russian Emerald (Source: Tsarina Jewels)
Ultimately, when buying a gemstone, what matters most is how it makes you feel. Remember, there is no such thing as a flawless gem, but at Precious Earth, we can assure you of finding the perfect one for you.
Are Gemstones With Inclusions Cheaper?
Usually, gemstones with visible inclusions are cheaper than those without flaws. The more the inclusions affect the 4Cs of a gemstone, the lower its price tends to be, generally speaking. To know more about the 4Cs of a natural gemstone, read this guide. That being said, some rare inclusions that enhance the appearance of a gemstone can increase the value and price of a gemstone.
Where Can I Buy Natural Gemstones Without Inclusions in India?
Natural gemstones without inclusions are extremely rare and usually cost a fortune. Natural gemstones with high clarity can be found both offline and online in India. At Precious Earth, we specialise in a wide range of precious gemstones such as diamonds, sapphires, rubies, emeralds, and pearls. We also offer semi-precious colored gemstones such as amethysts, aquamarines, moonstones, and opals. We ship natural gemstones all over India.
Where Can I Buy Natural Gemstones Without Inclusions Online?
Completely flawless natural gemstones are highly rare and hard to find online. At Precious Earth, we offer a wide range of coloured gemstones with a high level of clarity. We provide detailed descriptions and clear pictures so that you can examine the gemstone to your satisfaction. And if you are still sceptical, With our lifetime returns policy, rest assured of a genuine purchase every time.
