Gemstone facets play a significant role in a finished stone’s optical performance. They not only create various geometric patterns on a gemstone but also make it sparkle. There are different types of facets, and they all have specific names and functions, helping to choose a high-quality gem.
What Is a Gemstone Facet?
A facet is a polished surface, usually featuring three or four sides, cut to improve a gemstone’s appearance by optimising its optical performance and allowing it to reflect light. There are different types of facets, and each of them has a function. Some gather light from above, others disperse the entering light and reflect it back to the observer. Working together as a whole, facets make a diamond or any other gemstone sparkle creating a unique appearance.
The art of gemstone faceting traces back to 14th century Europe where lapidaries fully realised the potential of gemstones to reflect and refract light. That’s when they started to employ precise geometry in the development of various facet arrangements.
The ideal product of faceting is a gemstone that displays a colourful dispersion, commonly known as fire, internal reflections of white light known as brilliance, and coloured flashes of light from facet to facet towards the centre of the gem, known as scintillation.
It’s worth mentioning that faceting is usually applied to transparent to translucent material, although opaque gemstones, such as black diamonds, may also be faceted to produce appealing reflections.
Types of Gemstone Facets
Most gemstones share principal areas of faceting, which are girdle, crown and pavilion. The girdle is the gemstone’s middle portion, a narrow section separating the crown from the pavilion. It functions as a stone’s setting edge. The crown is the upper portion of a gem, from the table to the top edge of the girdle, while the pavilion is the lower portion of a gem, from the bottom edge of the girdle to the culet.
The crown facets include the table, crown mains, stars and upper halves, which gather and disperse light to create fire, brilliance and scintillation. The pavilion facets include lower halves, pavilion mains, and an optional culet, which reflect light back through the crown to the observer.
The table is the top horizontal facet on the crown of the gemstone, which is often the largest facet. It acts as a window and helps gather light from above and either reflects it back to the observer or directs light into the stone’s interior.
The main facets are both on the crown and pavilion of the gemstone. Crown mains, also known as bezels in the diamond trade, are the facets referring to a position between triangular facets bordering the table, known as stars, and upper girdle facets, touching the girdle from the top. Crown main facets usually feature a kite shape and touch the table and the edge of the girdle.
When there is more than one row of triangular or kite-shaped facets between the lower girdle facets and the culet or culet facets, those touching the culet area, the intermediary facets are called pavilion mains or mains. There can be several rows of facets in this area, and all of them can be referred to as mains, often adding confusion.
Break facets are bordering the girdle from the crown and pavilion. Break facets adjoining the girdle from the top of the gemstone are referred to as upper girdle or upper half facets, and those bordering the girdle from the bottom of the gem are called lower girdle facets or lower half facets in the diamond trade. Break facets scatter light, creating more scintillation and flashes of light.
Stars are triangular, top row facets bordering the table. They control the entry and exit of light from the gemstone.
The culet is a tiny facet at the bottom of the gemstone placed parallel to the table. It prevents chipping and abrasion to the point. Large culets are visible through the table as dark circles and allow light to escape through the bottom of a gem which negatively affects a stone’s light performance.
Many facet arrangements, primarily step cuts, do not feature a pointed or a flat culet facet. For example, the bottom of the emerald cut is still referred to as a culet, but the line that forms along the bottom of this arrangement is called a keel or keel line.
Meet and Meetpoint
There are also terms describing the area where facets meet. The term meet refers to the junction of two facets, while the meetpoint describes the junction of three or more facets.
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