The 3rd C of Sapphires: Cut
sapphire gemstone cut facets
The third factor that influences a sapphire’s quality is its cut. Akin to diamonds, sapphire in its natural state are not fit for commercial use, either as precious gemstones or as a part of a fine jewellery item. Hence sapphire when they are taken from their natural state, they are subjected to a prolonged process involving many stages to improve their quality. This process of value addition involves washing, shaping cutting and polishing the gemstone. The cutting process is an important step, that takes place under great care, with experts using special instruments, cutting them into a variety of shapes, including the popular ones that are used for diamond cutting: Emerald, Asscher, Oval, Cushion, Pear and Round shapes. A sapphire’s cut, as it is for any gemstone is a key component that determines its value. For in addition to the type of cut in question, the cut of the sapphire will vary with respect to its quality. A low-quality cut will fail or in some cases weaken the sapphire's other qualities, notably, it's colour. In fact, a great sapphire cut will not only help accentuate the natural qualities present in sapphire, but it could also potentially lessen other shortfalls, such as a higher number of blemishes that may weaken its clarity.
Sapphire Cutting: Points the Jewellers Consider
When it comes to the cutting of sapphires it is important to note that the principles that govern quality diamond cuts also apply in this context. Quality diamond cutting is built atop three main factors: Geometry, Surface Polish and the Accuracy of Faceting. Let’s look at each of these and understand their importance for producing a quality sapphire cut, that helps preserve and accentuate the gemstone’s natural qualities.
Geometry
In gemstone cutting achieving a solid geometry of shape is arguably the most significant variable. The nature of the cut, in addition to bringing forth the desired type of cut (i.e. Round, Pear, Asscher) helps determine the geometry of the gemstone. This is a careful process involving the study and application of lengths, angles, proportions and areas to the shaping of the gemstone. Once the fundamental geometric shape of the gemstone has been decided upon the next two factors that follow are its symmetry and proportions. The symmetric of the stone deals with the correct alignment of the gemstone’s facets (the many numbers of small flat surfaces on the shape of the diamond). A well-cut sapphire will have great symmetry where the facets of the gemstone meet, without inconsistencies on the points of convergence.
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Proportions
The next key factor affecting the gemstone’s cut is its proportions, which deals with the diamond’s crown height, crown angle, pavilion depth, pavilion angle, table size etc. However, in the industry, there are a number of competing frameworks that decide on the acceptable numbers that seek to standardize this framework of measurement. The standard proportions of the diamonds whilst differing with respect to the type of international measure that is being used, however, align in relation to the quality of the cut, with respect to the proportions, which deal with how light. One that is Understood at three levels, whereby gemstone cuts are graded. From shallow, and deep to ideal cuts.
The Depth of the Gemstone’s Cut
The grading of diamond cuts should not be confused with the different shapes and cuts of diamonds. For each of the gemstone's shapes, there is are set of proportions and critical angles that a diamond should be cut to in order to maximize its brilliance, fire and scintillation. In the same way, the closer the sapphire is cut to meet these standards, the more brilliant it will be. Gemstones like diamonds that are poorly cut may appear bright in jewellery stores under strong lights, but they may appear weak in dim or normal lighting conditions. A key marker of diamond quality is the quality of the cut that the stone is measured in relation to the depth of its pavilion. Which in turn is a reflection of the gemstone’s overall proportions. A well-proportioned pavilion is positively correlated to its level of brilliance. Naturally, a shallow or high depth in the pavilion of the gemstone will cause light to leak out at the critical or the largest angle of the gemstone. Unlike a gemstone that is cut in an ideal shape, which reflects back the light from within it, back upward towards the table. In shallow and deep cuts, light rays that hit the gemstone will escape from a particular region (i.e. the wider or deeper pavilions), weakening its brilliance: which is the combined effect white light produces as it hits the surface of the gemstone.
Surface Polish
In the world of diamonds, the quality of the gemstone’s polish has been set by the GIA. Where the quality of the gemstone is measured on a scale that grades the diamond’s polish based on the visibility of polished lines, and blemishes on the surfaces of the stone. The quality of the gemstone’s polish is determined by gemologists using magnification tools. The surface polish of sapphire can also be measured in similar ways. When determining the polish grade, Excellent grade gemstones have no visible polished lines and other blemishes, where the entry of light is not inhibited, with no effects on the gemstone’s sparkle or brilliance. Features that weaken as the quality of the surface polish moves to lower grades. In sapphires, things get a bit more tricky. Whilst the same principles on surface polish apply. However, since sapphires often tend to be found in smaller sizes than diamonds, and are colour concentrated, the cutter needs to exercise greater caution. Sometimes a weaker polish may be better in relation to the carat and colour quality of the stone.
Accuracy of Faceting
Gemstones can be cut using traditional cutting tools or commercial equipment. In recent times gem cutting has benefited from the addition of modern technologies allowing precision cutting methods. The art of lapidary is an ancient one. It is a process that has been refined and improved over the ages. Today a new technique has entered the gemstone cutting fray, one that is widely used in the world of diamonds and is also adopted in sapphire cutting practices: Precision faceting. Which is a type of gemstone cutting that uses precision tools, that are computer-guided and are carried out with extreme care, and usually at the cost of manual labour. Precision cutting tends to place a higher emphasis on gemstone quality, in terms of minimizing blemishes and optimizing its brilliance, with maintaining the carat of the gemstone coming in at a later stage.
In the world of sapphires where the carat and colour of the gemstone dominate, precision cutting tends to be used with commercial cutting methods, with the latter being prioritised. For reasons, as we shall see, in the sapphire cutting world, the focus of the cutter tends to narrow to increasing the quality of the colour of the sapphire and maintaining a larger carat, which in turn will require a more piratical, less precise cutting approach to cutting and faceting of the gemstone.
Hurdles in Gemstone Faceting
Gemstone faceting can seem like a straightforward process if the jeweller in question has the services of an expert craftsman. But no matter the quality and experience of the craftsman there are a few hurdles that he must navigate in producing a great gemstone cut, that qualifies in terms of its ability to maintain solid colour, clear facets, well-defined shape and meaningful carat, depending on the original size of the rough stone. Here is a list of issues the gemstone crafter needs to be aware of in producing a top-quality gemstone cut.
Uneven Girdles
In crafting a finely cut gemstone jewellers must ensure to meet an optimal girdle size. The girdle is the important area that sits between the gemstone’s pavilion and crown, and its size affects the overall visual character of the gemstone. The key is to avoid the extremes of a very thin girdle or a thick one. A thin girdle leaves the gemstone corners vulnerable to chipping, and in certain gemstone cuts like princess cuts, which have sharp edges this could be problematic. Thicker girdles are somewhat more acceptable than thin ones, as these can provide that added heft to the sides of the cut stone. However with higher thickness of the girdle comes the disadvantage of greater difficulty in setting the gemstone in place, depending on the engagement ring in question, and it also adds to the total carat of the stone without enhancing its visual character.
Too Many Facets
Generally, the number of facets and their placement generally depends on the cut of the gemstone: with princess cut diamond cuts ranging from 50 to 58. Round cuts tend to stay at a fixed 58 facets, with the now popular trillion cut stones also featuring a fixed number, but this time coming in at 50 facets. An important point to consider when it comes to gemstone faceting is that their number can vary. As noted certain diamond cuts, like the princess cut, which are technically diamond shapes, can vary in terms of their total number of facets. The key point to consider is the carat of the gemstone and the crafting freedom it provides in line with other factors like the colour of the gemstone. Which in the world of gemstones is often a feature of fancy coloured diamonds. Having too many facets on a smaller gemstone will have the adverse effect of reversing the visibility of the facets. Since faceting is done to enhance the light reflecting qualities of the stone, notably its brilliance, too many facets on a smaller stone, will counter this effect. The faceting of the gemstone must work in proportion to the carat of the stone: certain smaller gemstones, such as those reserved for accent stones best limited to facets that fall between 15 – 20. But larger, 0.5 to 1.0 and above can feature a higher number of facets 50 – 58 mark but still vary in accordance to the style of the stone. As certain gemstone shapes, like emerald cuts, are such candidates.
Features of a Well Cut Sapphire
The thing about sapphires cuts is that there are no fixed standards. Whilst the major gemstone cuts also apply to those of sapphires, the difference is the subtle variations that enter the sapphire cutting process. So while the key principles that govern a quality diamond cut remain, cuts are often personalized, depending on the individual character of the stone. And all this starts with a good quality cabochon, which is cut to accentuate its ability to interact with light. If you read our Education page on the 1st C: Colour, you will know that light is the central variable that determines the visual quality of the gemstone. A well-cut sapphire will have an even table on the crown of the gem, with all of its facets being symmetrical. The depth of a cut sapphire often varies according to its colour tones. As jewellers understand the importance of the role played by light, and hence shape and the facets of the gemstone, in accordance to the colour of the gemstone. With light-coloured sapphires often having a deeper cut to add depth to their colour, conversely darker sapphires take on a shallower cut, to permit more light into the gem and increase reflection increasing its brightness.
Sapphire Cutting is a Balancing Act
Since colour is an important variable in sapphire cutting, once the depth of the gemstone cut (shallow, deep, or ideal) has been determined, the cutter must take into consideration the presence of colour within the corundum crystal. Since sapphires have a different refractive index than carbon-based stones, these particular gemstones need to be faceted in a particular way to optimize light reflection, but at the same time to show the gemstone’s colour more strongly. This means when it comes to the process of gemstone cutting there are necessary trade-offs that the cutter must deal with. Which mainly involves those between sapphire cut and carat and sapphire cut and its colour. All of this would depend on the quality of the stone, however, given the rarity of sapphires, particularly the good ones with solid colour, and a decent carat to start with (note: In the world sapphires are rarer than diamonds)
Cut vs Carat
This is the main trade-off. One that divides the good gem cutters from the best. Cutting a gemstone essentially means bringing it down to size and value. However, the cutting of the sapphire is a requirement that determines the saleable value of the gemstone, either individually or as part of a fine jewellery item. So once the type of cut has been selected, deciding the symmetry of the gemstone will necessarily involve making sacrifices to the final carat the sapphire. As the jeweller cuts away parts of the stone to bring about the desired shape, there is a necessary trade-off between the carat (i.e. the overall weight of the gemstone). Hence the jeweller who seeks to maintain a larger carat for the sapphire is likely to make adjustments to the cut to maintain a greater weight, hence the size of the gemstone. Which may affect the final quality of the cut. A matter that is made more difficult by the presence of colour in the gemstone.
Cut vs Colour
In sapphires, things are a bit different since a key factor in the quality is its colour. So whilst there is a degree of loss to the level of light that can be attained via an ideal cut, or by avoiding a shallow or deep cut. Jewellers who work with this gemstone are on the lookout for finding and maximising the colour in the gemstone. Which is often concentrated in a certain part of the sapphire, hence the cut of the gemstone is determined by this factor: making it shallower or deeper. Thus sacrifices may have to be made to the quality of the final cut. Since colour in a gemstone is not uniformly present and instead is located in certain zones (colour zoning), the cutter must seek to maximise the colour prevalent location within the gemstone, which in turn will come to determine the shape of the gemstone, with respect to its proportions. Which in turn may adversely affect the quality of the shape (i.e. a more shallow or deep cut) of the gemstone. Since the jeweller is required to balance two objectives at this point: a good cut, and the glowing colour of the stone.
Sapphire Cutting and Quality: Gemstone Dependent
The quality of the sapphire cut ultimately comes down to two key factors: the quality of the rough sapphire and the skill level of the cutter/jeweller. No two sapphires are the same, and no two coloured gemstones are the same. As one of the rarest minerals in the world, rarer even than the dominant diamonds, sapphires in their rough state require a great deal of care and attention as they are shaped, cut, polished and brought to the standard of a top-quality gemstone. Bringing forth a top-quality sapphire that commands a great cut that enhances the light reflective character of the stone, and is able to showcase the natural colour of the sapphire, whilst maintaining an acceptable carat, and proportion is a game of trade-offs. Each and every step in the process of gem cutting requiring optimisations in one area, whilst not compromising too much in another. The ability of the cutter to produce a great cut, in light of these limitations comes down to his experience and ability. As the reader may have noticed the process of sapphire cutting essentially builds on the fundamentals of diamond cutting, but owing to a number of key differences present in the character of the gemstone, and their availability in the required sizes, results in certain adjustments being made to the process. So additions and refinements are made to the process of gemstone cutting, in light of the distinct feature of sapphires. Notably, they are:
Mixed Cut
Mixed cuts combine step cut and brilliant cut styles. They have brilliant facets on the crown and step facets on the pavilion or vice versa. Mixed cuts may even combine different faceting techniques to produce a unique style. Faceters (i.e. those who do the faceting) can combine the above cutting styles to produce different gemstone shapes. For example, the famous princess cut is the product of carefully modifying a brilliant-cut gemstone. In line with this practice, gem cutters over the years have introduced a number of innovations, such as Asscher Cut, is which is a product of combing existing types of cuts. In the world of sapphires, since the colour is a key driver in determining diamond shape and cut, many new variations can be found in addition to the popular gemstone cut types.
Ceylon Cut
Considered as an indigenous cut with origins in the land of gems, Ceylon cut sapphires are known for their non-symmetrical pavilions. These cuts are partly a product of the socio-economics of the gem trade in Ceylon, which we cannot get into here. However, gemstone cutting, especially when it comes to sapphires is governed by a degree of pragmatism of the jewellers in this part of the world, where maintaining perfect geometry is not always the top priority for the cutters. A prevalent feature of Ceylon cut sapphires is the step-cut pavilion which either follows or precedes a brilliant cut. The combining of cuts to attain a desired shape often veers towards maintaining a larger carat, whilst maintaining a degree of symmetry that supports adequate proportions is an acceptable practice. One that goes in line with the need to increase the effects of the sapphire’s colours.
Sapphire Cuts and Engagement Rings
When it come to engagement rings, a key selling point for sapphires and gemstone, in general, the quality and character of the cut. One that is much dependent on the character of the ring design. The structure of the band and the manner in which the gemstone has been mounted will affect the choice of sapphire cut. Certain engagement ring designs, such as those with Tension settings, or Cathedral settings that provide great emphasis on the stone may require a higher quality cut. Given the visual focus on the character of the stone, an ideal cut is more suitable, as the visibility of shallow and deeper cuts will affect its overall quality. Hence when it comes to sapphire engagement ring, the quality of the gemstone, in terms of its cut, colour and carat is will affect the kind of ring design one may choose.
Cabochon Cut & Star Sapphires
Star sapphires are an interesting addition to the sapphire family. Since star sapphire’s stand out feature is the asterism. Which are the star-like white marks on the surface of the gemstone, a rare and much sought after effect in the world of gems. In such sapphires, the gemstones must be cut as a cabochon, rather than be subjected to traditional cutting methods, in order to display its asterism. A finished star sapphire's quality and value depends on the star’s orientation; which is determined by the quality of cabochon’s symmetry and proportions. For a start, the faceting of a star sapphire gemstone is almost always out of the question. The cabochon cut is aimed to carefully centre the star of the gem, whilst keeping the gemstone’s outline symmetrical. Star sapphires often come with a dome shape, which needs to be cut in relation to other qualities of the gemstone. So the cutting of star sapphires is a distinct art in the world of sapphire cutting.
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