Diamond Inclusions Clarified

If you are in any way familiar with diamond certification and diamond quality you are likely to encounter the term ‘clarity’. Diamond clarity is a key determinant of diamond quality that makes up one of the 4Cs. The higher the clarity of the stone, the better the clarity grade, and in turn the value that is attached to it, and naturally the price point of the diamond in question.

When it comes to determining diamond quality with respect to clarity the key variable is the role of inclusions. Inclusions are generally bad, and diamond cutters and top jewellery companies rate the quality of the stone based on the absence or rarity of inclusions.

In this Education page, we will break down what is meant by inclusions, explain the various types of inclusions that are out there, and what diamonds and diamond jewellery buyers need to consider when seeking a top-quality diamond.

What is an Inclusion?

In simple terms inclusions are irrationalities and inconsistencies of whatever type that find themselves within and on the surface of a diamond or gemstone. The term inclusions are mainly applied in relation to carbon-based gemstones like diamonds, since it is only with diamonds, that the official gemstone classification (4Cs) includes clarity as a key quality factor, where they have become better recognised. However, the term inclusion applies to all top gemstones that are traded in the world of gems and gemstone jewellery.

When it comes to inclusions, the term technically only refers to internal breaks, and other types of inconsistencies-which we shall get to-that are present in the diamond or other gemstone. However, the term inclusion is often used as a general term under which all negative features affect the integrity of a diamond or gemstone, either internally or externally, with the exception of the gemstone’s colour. This means external gemstone inconsistencies like blemishes are also generally included under the heading of ‘inclusion’. However, the term inclusion can refer to a number of different types and not all inclusions are the same with respect to effect and extent.

Origins of Inclusions

Since inclusions are features in gemstones that exist either as impurities, breaks, chips or as external materials that disrupt or adversely affect the structural integrity of the gemstone, the question is where do they come from? To answer this question we need to look at the origins of gemstones. The top gemstones in the world, from diamonds to sapphires to rubies and emeralds are the result of mineralogical processes that take place deep underground. In the case of diamonds, the combining of carbon atoms to form the particular bonds that result in hardened crystals takes place hundreds of miles underground, they emerge as a result of extreme heat and pressure.

As you can imagine this process is not perfect, with the actual process of development of the various gems being driven by volcanic processes. Thus imperfections are bound to arise. From irregularities to the structure of the gemstone, to entry of trace minerals, to other types of shortfalls. In addition, with gemstones, once they have taken form, they generally undergo an arduous process of going from deep ground to reaching closer to the surface. These can a number of different forms such as faulting, volcanic eruptions, soil erosions, metamorphic processes like plate tectonics, etc. And all exert some kind of effect on the integrity of the stone.

During the course of such events that take place over various lengths of time, the gemstones, which are generally found in or within other types of rock formations, like igneous rocks and alluvial deposits, but also in sedimentary other rock formations, come to be affected by these. This is why gemstone value in the marketplace is not just a function of the type or rarity of the stone, but its gemstone quality in terms of the carat, quality of color, and structural unity of the stone. For example, a 3.00-carat diamond that is filled with internal breaks and external blemishes is likely to find only a few buyers.

Type of Gemstone Inclusions

It might be interesting to note that not all inclusions are the same. Inclusions can vary in terms of type and extent and sometimes could even vary with respect to the type of gemstone in question. Among the most common type of inclusions are:

  • Needles: Arguably one of the most common types of inclusions found in gemstones. These long thin needle-like inclusions are generally found within diamonds. They can appear as individual needle-like lines or may appear as clusters. Basically the higher the number of such needles the lower the quality of the stone.

  • Pinpoint inclusions: Pinpoints are referred to tiny disruptions found within the gemstone, that take shape of tiny crystals present that find themselves within a hardened crystal. These types of inclusions can also be individually or in clusters.

  • Foreign crystals: This should be self-explanatory and they refer to external crystals that are other types of hardened materials or even tiny diamonds that have formed or entered the main gemstone.

  • Clouds: Clouds are an interesting phenomenon that appears as a white or light haze that affects the transparency of the stone, affecting the amount of light that passes through the gemstone thus affecting its reflective qualities.

  • Knots: Knots technically fall under blemishes, as they refer to crystal inclusions that exist on the surface of the diamond, which is shaped as a knot. Surface blemishes of any kind are generally undesirable and knots are no exception.

  • Chips and Cavities: Akin to the world of dental health, diamonds also feature imperfections in the form of tiny holes and slight breaks on the surface and internal drills. These are often tiny but are significant enough to affect the quality of the stone.

  • Graining: Diamonds form as a result of hardening carbon atoms that unite to form a strict covalent bond. This unique crystal lattice structure is what gives diamonds their durability and value. Graining is an internal inclusion that results due to irregular crystal growth, where there is a lack of structural uniformity within the gemstone. These types of inclusions are visible upon microscopic analysis and take the form of a white haze.

  • Feathers: Features are basically cracks that form within the stone that looks like feathers. These are not a net positive for in addition to affecting the internal clarity of the stone, they also undermine the integrity of the diamond, weakening its overall durability. And depending on whether these features are located they can further undermine the visual character of the stone.

  • Man-Made Inclusions or Etches: Other types of inclusions to look out for are etches: which are tiny marks on the surface of the stone, which are often a result of poor cutting and shaping of the stone, and could affect its quality.

External ‘Inclusions’ or Blemishes

The difference between inclusions that are specific to the internal structure of the stone and blemishes or external inclusions (though this term is not generally used) exists to distinguish between two top diamond clarity grades: Flawless Diamonds (FL) and Internally Flawless Diamonds (IF). The latter (FL) is known to feature no internal breaks that are visible to the naked eye or even under 10x magnification. The latter (IF) however whilst being internally sound, does contain surface inconsistencies or blemishes.

Inclusions in Synthetic Gemstones

A related field in the development of diamonds and other top gemstones is the rise in synthetic variants. These lab-grown alternatives to natural gemstones are not without their own set of issues, which can take the form of inclusions. The kind of inclusions that are featured in artificial stones tends to depend on the kind of development they have undergone. Which could be similar but also unlike those found in naturally sourced gemstones. These artificial inclusions could take the form: of light shading on the stone, that affects the gem's translucence, or add a very degree of opacity. Or sometimes even feature spider-like webs.

‘Fancy' Inclusions

This is an emerging field in measuring diamond quality that tries to view certain types of inclusions as a positive trait. This is not a uniform practice, and they are developing areas of interest. Basically what we are dealing with is a certain type of diamond inclusions, that feature inclusions that are present as distinct markers: known as salt and pepper inclusions, these add a distinct effect to the diamond, giving it a distinct feel, and making it stand out from conventional diamond types. The distinct look of these diamonds makes them a niche interest for diamond jewellery buyers.

In other top gemstone types like sapphire and rubies, there is a phenomenon called asterism: which refers to rutile or needle-like inclusions that form in specific areas of the stone and do so in a concentrated form to produce a star-like effect. Or a similar but different effect like cat’s eye, which is a feature in cabochon gemstones.