Coloured gemstones, with their captivating colors and inherent beauty, have fascinated humanity for centuries. Within the rich variety of the world's precious and semi-precious stones, which include blue sapphires, amethysts, garnets, peridot, quartz, citrine, beryl, zircon, opals, moonstones, and more, each possesses a unique allure in the realm of gems and jewelry. As we explore these gems, it becomes essential to distinguish between two factors that can affect their overall visual appeal and structural integrity: inclusions and internal cracks.
Although generally subtle, inclusions and cracks play a significant role in determining the quality and value of gemstones. This article seeks to demystify these imperfections, providing insights into their characteristics, methods of identification, and the treatment processes employed to enhance or mitigate their impact. Keep reading to understand everything you need to know about gemstone inclusions and internal cracks.
What Are Gemstone Cracks & Inclusions?
Cracks are structural irregularities within a gem that result in visible lines or fissures on its surface. These result from external factors like pressure, temperature changes, or handling during the gemstone's formation process.
Inclusions, in contrast, are internal imperfections within the gemstone. They are inherent and form during the gemstone's natural growing processes. Inclusions may or may not be visible on the surface and can include minerals, gas bubbles, or other materials trapped within a gem during its formation.
Inclusions and cracks are both significant factors that affect the clarity of a gemstone. Clarity pertains to the internal characteristics, such as inclusions, within the gem and external blemishes such as cracks on the stone. In general, the fewer cracks and inclusions a gem has, the higher its transparency, and thereby higher its value. Inclusions are more difficult to get rid of to increase a gem’s transparency, whereas external cracks can be easily fixed by polishing or precise gem cutting. For some connoisseurs, however, certain types of inclusions add to the beauty of the stone, and they may be willing to pay an additional amount to acquire such a gem.
Gemstone Cracks vs. Inclusions
Differentiating Between Gemstone Cracks & Inclusions
- Surface Reach & Location: Gemstone cracks, may originate internally or externally, and often manifest in regions where the gem's inherent physical structure or composition is less robust. Typically, these are the outer edges of a gem, particularly in proximity to the metal settings of jewelry. The susceptibility of these edges, especially when surrounded by metal, makes them more prone to developing cracks and gems with a larger carat weight are more prone to cracks. Conversely, inclusions, which are natural impurities embedded within gemstones, remain internally positioned without altering their locations. They are usually trapped within a gem during its formation process over millions of years. Understanding these distinctions is crucial for gemmologists and enthusiasts alike, aiding in the accurate evaluation of a gem's condition and value.
- Causation: Inclusions in precious and semi-precious stones are typically inherent to their growth processes – when they are formed under the surface of the earth and in the vicinity of a plethora of different solids, gases, and liquids. Conversely, cracks generally result from external pressure, regular wear and tear, or rough handling, such as heavy cutting or improper jewellery settings. These cracks may manifest on the outer surface or within the gemstone itself. Some gemstones, mainly those that are naturally brittle, like pearls, aquamarines, precious red corals, and emeralds, are more susceptible to cracking. However, even gemstones that are not inherently fragile, such as moonstones, opals, or sapphires, can develop cracks when subjected to rough handling or external forces.
- Development: Inclusions are natural features in precious gemstones, forming during their initial development and contributing to their rarity and value. Cracks can sometimes be irregular developments of inclusions, surfacing later in a gemstone's life. If an imperfection goes unnoticed initially and appears over time, it is likely a crack, often caused by mishandling or carelessness. Depending on the type, sometimes certain inclusions are celebrated for adding uniqueness to a gem, while cracks are more indicative of external stress and should be detected early for proper care.
- Characteristics: The appearance and structure of inclusions can vary due to their natural origin, in contrast to cracks, which lack such features and exhibit uniformity. Inclusions can be made of solids, liquids, or gases, and can be discerned by holding your opal, moonstone, turquoise, or other gemstone up to direct bright light. Rotating the stone and viewing it in different angles helps in distinguishing between a crack and an inclusion. If there is a crack, you'll observe that light reflects off it, similar to a windscreen chip. These represent some of the most apparent distinctions between inclusions and cracks. Further, studying the inclusions of a gemstone can help identify its origin, which is an important consideration of quality in coloured gemstones.
Inclusions vs. Cracks in a Yellow Sapphire
Do All Gemstones Contain Inclusions?
As a general rule of thumb, it is important to understand that over 95% of all gemstones in the market contain some type or form of an inclusion, and that the fewer inclusions a gem exhibits, the higher its value. Authentic and original precious gemstones hold higher value and rarity than counterfeit or synthetic counterparts, and can often be differentiated by studying their inclusions. In gemstone jewelry, inclusions may vary in visibility depending on the carat weight of the stone and other factors - sometimes apparent to the naked eye and sometimes requiring magnification.
Although precious stones with fewer inclusions are generally preferred to those with more inclusions, certain types of stones and inclusions are actually desired for these traits. These natural imperfections in gems like opal, amethyst, moonstone, or turquoise often contribute to their value and rarity. The tiny spheres of silica in opals, for example, are responsible for producing a phenomenal optical effect known as the “play of colour” – which is an important determinant of the value of an opal. As another example – blue sapphires may contain silk inclusions, which are tiny rutile needles that add a delicate, ethereal quality to the stone. Further, emeralds exhibit “jardin”, which are characteristic inclusions resembling garden-like patterns within the gem. Moonstone, known for its enchanting glow, showcases tiny tension cracks referred to as centipedes, further enhancing its allure.
A White Opal with a strong Play of Colour effect that occurs due to tiny silica inclusions
Treating Cracks & Inclusions
Sometimes, gemstone inclusions or cracks can undergo treatments based on their type and location. Different stones respond differently to specific treatments; for instance, silk-like inclusions can be addressed through thermal enhancement, where high heat melts the silky rutile needles, enhancing the stone's clarity. Surface-level cracks might be eliminated by polishing, restoring the gem's surface quality. As such, not all treatments apply universally to all gem types. Every stone has specific treatments suitable for its enhancement. Understanding these distinctions is crucial in determining the best approach for treating imperfections and preserving the gem's value and appearance.
Treating Cracks
- Filling: It is a common method to reinforce gemstones by stabilizing fractures, preventing further propagation of cracks, and enhancing their resistance to damage. An effective technique involves using epoxy or Opticon to fill the cracks in gemstones, providing durability and support. Oiling is part of the crack-filling process to reduce the visibility of surface-reaching fissures, cracks, crevices, and other dislocation features in gemstones. It helps enhance the overall appearance and durability of the treated gemstone, providing a glossy finish and minimizing the visual impact of cracks. Notably, emeralds often undergo oil filling, where natural oils fill fractures and enhance the gemstone's clarity.
- Polishing & Lapidary Work: This crucial treatment involves grinding, sanding, cutting, and polishing gemstone surfaces post-crack filling, ensuring a flawless appearance, structural integrity, and overall aesthetic appeal.
Treating Inclusions
- Heat Treatment: This common gemstone enhancement involves applying heat to a gem to alter its color, clarity, or optical properties. It is a widely used method for various gemstones to enhance their visual appeal. It is used on various gemstones, including sapphire, corundum, zircon garnet, and citrine. Amethysts treated with heat, for example, can produce green quartz and citrine.
- Laser Drilling: A technique primarily used on precious stones like diamonds, laser drilling involves using a focused laser beam to create channels from the surface to reach inclusions. This process is often followed by introducing chemicals to alter the appearance of inclusions within diamonds.
- Surface Coating: Precious stones, including diamonds, can undergo surface coating treatments. This process involves applying a thin material layer on the surface to enhance color or modify certain characteristics. It's commonly used to address dark inclusions in diamonds after laser drilling.
- Diffusion Treatment: Diffusion treatments involve heating the gemstone to an almost melting point. Diffusion treatments heat gemstones close to melting (e.g., in corundum up to 1500°), causing molecular structure loosening. This enables chemicals to enter, penetrating the surface and near-surface areas, becoming part of the crystal structure. Diffusion is a slow process, mainly impacting a shallow layer. Generally, the chemicals used are natural components of the gemstones. For example, sapphires are mostly heated with beryllium powder to enhance their blue color.
An artisan using a blow-heat method to thermally enhance rubies (Image Source: GIA)
It is important to note that these different types of treatments of cracks and inclusions in a gemstone can yield different results. Some treatments, such as thermal enhancement or heat treatment are permanent and do not have any impact on the structural integrity of a gem, but other treatments such as surface coating may be temporary and may fade over time. As such, it is always wise to consult an experiences and reputable gemologist before your purchase, and always ensure you receive a certificate of authenticity from your supplier that discloses any and all treatments that a gem may have undergone. This ensures a well-informed purchasing decision.
Conclusive Reflections
Recognizing the distinction between gemstone cracks and inclusions holds paramount importance when making investments in gemstone jewelry, guaranteeing the procurement of genuine and alluring pieces. The choice of a reputable vendor substantially diminishes the likelihood of acquiring counterfeit gemstones, and in this aspect, Precious Earth stands out.
Being a part of the gem trade for over 80 years, we provide a diverse array of options, encompassing exquisite blue sapphires, zircons, opals, aquamarines, moonstones, and more with over 2000 gemstones across 20+ categories in our inventory. Within our extensive selection, you can confidently choose a gemstone that aligns with your preferences, ensuring both a visually captivating purchase and a secure long-term investment.
