Gemstone Clarity and Inclusions Explained

Introduction

Look closely into almost any gemstone and you will find something hidden inside it: a tiny crystal of another mineral, a spray of fine needles, a droplet of fluid trapped while the stone was still growing, or a fracture that healed over long ago. Gemologists call these internal features inclusions, a term that also covers features reaching the surface from within. Marks confined to the surface itself, such as scratches, nicks and polishing lines, are called blemishes. Clarity describes the relative absence of both, and how much they affect the way a stone looks.

What counts as good clarity depends very much on the gem. Topaz is routinely found with no inclusions visible to the naked eye, while an emerald that looks equally clean is exceptional. An ordinary expectation for one stone can be a genuine rarity in another.

This is why clarity is more than a simple ladder running from “included” to “flawless.” To read a clarity description properly, you need to know which gemstone it refers to, how the stone was examined, and which grading system is being used.

A Short History of Clarity Grading

For a long time, the trade had no shared language for clarity. Jewelers described diamonds as “perfect,” “loupe clean” or “piqué,” and some already used abbreviations such as VVS and VS, but none of these terms had an agreed definition. The same word could mean quite different things from one seller to the next.

The change came from the Gemological Institute of America (GIA) in the early 1950s. Under its executive director, Richard T. Liddicoat, the institute introduced its D-to-Z color scale in 1953, and the clarity scale that Liddicoat developed with his colleague Lester Benson was refined over the following years. GIA’s laboratory issued its first diamond grading report in 1955. For the first time, jewelers had defined grades, a standard way of examining a stone and a common vocabulary, and the trade still relies on that framework today.

The Diamond Clarity Scale

The GIA clarity scale for natural diamonds has eleven grades, grouped into six categories. Every grade refers to what a skilled grader sees under 10× magnification.

Within each category, the lower number means the higher clarity, so a VS1 diamond is slightly cleaner than a VS2.

The difference between the two top grades is a useful one. A Flawless diamond shows neither inclusions nor blemishes at 10×, while an Internally Flawless stone has no inclusions but does show minor surface blemishes, which could often be removed by repolishing. Both are observational grades. They describe what can be seen at the standard magnification and are not a claim that the crystal is perfect at every possible level of detail.

To arrive at a grade, the grader weighs five factors: the size, number, position and nature of the clarity characteristics, and their color or relief. Relief is the contrast between a feature and the surrounding diamond, and it largely decides how conspicuous that feature is. A grader may use higher magnification to identify what an inclusion actually is, but the grade itself is always based on its appearance at 10×.

Clarity in Colored Gemstones

The diamond abbreviations VVS, VS, SI and I are also used for colored stones, but they do not carry the same meaning. Colored gemstones are formed under very different geological conditions, and many varieties are almost never free of inclusions. A clarity standard designed for diamond would place most emeralds near the bottom of the scale, which says little about how good an emerald actually is.

GIA’s educational grading framework handles this by sorting colored gemstones into three clarity types, based on how included each variety normally is.

The grade definitions then shift with the type. A VS grade in a Type I gem describes inclusions that are minor and somewhat easy to see at 10×, while in a Type III gem the same VS describes obvious inclusions that may even be visible to the eye. Identical abbreviations therefore do not describe identical stones. A clarity type is an expectation for a variety, not a verdict on an individual gem, and a Type III emerald can still be an exceptionally clean example of its kind.

Tourmaline shows why color matters so much here. Green tourmaline is expected to be eye-clean and sits in Type I, most other colors fall in Type II, and red and watermelon material belongs to Type III. Pink tourmaline also commonly shows eye-visible inclusions. None of this prevents a particular red or watermelon stone from being beautifully clean.

You will sometimes see IF applied to colored stones that a seller judges free of inclusions at 10×. GIA’s colored stone framework does not include an IF grade, so this is a commercial description, and its meaning should be explained by whoever uses it. It is also worth knowing that GIA’s laboratory reports for colored stones do not assign clarity grades at all. They identify the species and variety, any detectable treatments and, on request, the geographic origin.

Clarity Grades by Type

Put the grades and the types together and the same letters start to describe quite different stones. Each row of the table is one grade and each column one clarity type. Every cell gives two things: how the stone looks to the unaided eye, and what a grader sees with a 10× loupe.

So an SI1 tanzanite, an SI1 ruby and an SI1 emerald are three very different stones. In the tanzanite, a Type I gem, SI1 means inclusions you can only just make out without a loupe. In the emerald, a Type III gem, the same grade allows inclusions that are the first thing you notice. Each stone is judged against what is normal for its own kind.

Commercial Letter Ratings

Labels such as A, AA, AAA and AAAA are quality categories defined by individual sellers. They often blend color, clarity and cutting into a single rating, and the criteria change from one business to another. There is no universal A-to-AAAA standard for colored gemstones.

A clearly explained letter system can be useful for comparing stones within one seller’s inventory, but an “AAA” gem from one shop cannot reliably be compared with an “AAA” gem from another. A plain description of the color, the inclusions present, the polish and any damage tells you far more.

Clarity Across Different Gemstones

The table below sets out the clarity type, the typical appearance of faceted material and the most common inclusions for a range of popular gemstones. Many of the inclusions listed are visible only under magnification, even in stones that look clean to the eye. A dash marks gems that are not included in GIA’s published clarity-type lists.

Two patterns stand out. First, the clarity type describes a broad tendency for the whole variety, while the descriptions in the table reflect material selected for faceting. That is why Type II gems such as amethyst and citrine are still often eye-clean in the stones you actually see in jewelry. Second, confetti sunstone and strawberry quartz sit outside ordinary clarity grading altogether, because their inclusions are the very reason people want them.

How Inclusions Affect Beauty and Value

How much an inclusion matters depends on how noticeable it is and where it sits. A small crystal near the edge of a stone may have almost no effect on its appearance, while a prominent inclusion right under the table, the large flat facet on top, catches the eye immediately. Dense clouds of tiny inclusions can reduce transparency, and large fractures, especially those that reach the surface, can weaken a stone. The number of inclusions alone does not decide durability. Their nature, size and position matter far more.

Some inclusions are the whole point. In confetti sunstone, a feldspar, countless thin platelets of iron oxide, mostly hematite, lie scattered through the stone. As it moves, each platelet catches the light and flashes orange or copper, an effect called aventurescence. The larger and more numerous the platelets, the stronger the confetti sparkle, so here more inclusions make a better stone.

Strawberry quartz owes its name to its inclusions, which look like seeds scattered across a strawberry: red flakes and needles of iron oxide, generally hematite and lepidocrocite, caught in colorless quartz as it grew.

Insects caught in amber make a piece especially interesting to collectors. Quartz containing tiny droplets of petroleum is another favorite: the oil inclusions can glow vividly under long-wave ultraviolet light (LW UV). In stones like these, the inclusion is the main attraction.

Inclusions are also responsible for some of the most admired optical effects. When fine needles or tubes are aligned in the right way and the stone is cut as a cabochon, they reflect light into the six-rayed star of a star sapphire or the sharp line of a cat’s-eye chrysoberyl. Such stones are judged by the strength and beauty of the effect, which a clarity scale built for transparent faceted gems cannot capture.

For most colored gemstones, clarity is best judged together with color, cut and overall appearance. A richly colored stone with a few unobtrusive inclusions can be more attractive, and more valuable, than a cleaner one with weak color. Amethyst illustrates this well, as deeply colored material remains desirable even with some visible inclusions. When color and everything else are comparable, though, the cleaner stone is generally preferred.

Conclusion

A clarity grade is only as useful as the explanation behind it: what was seen, at what magnification, and under which grading system. The same abbreviation can mean one thing for a diamond and something quite different for an emerald or a tourmaline, and an eye-clean gem may still hold a whole world of inclusions under the loupe.

A gemstone’s appeal comes from the combination of its color, transparency, cut and individual character. Understanding clarity helps us appreciate both the exceptionally clean stones and those whose inclusions are part of their beauty. If you would like to see that range for yourself, our collections include both eye-clean gems and stones with characterful inclusions, each described with its clarity and treatment status.