A Glossary & Guide to Professional Diamond Terminology
When studying gemology or even simply selecting and purchasing a diamond, aside from the 4Cs, it is also incredibly useful to understand the correct terminology for the different parts of a diamond. Having knowledge of the diamond anatomy will not only let you understand your diamond expert or gemologist’s explanation and analysis better, you could also describe your requirements more accurately and precisely.
In this month’s blog entry, we give you a quick guide to the correct terminology of a diamond’s anatomy, taking the most popular diamond cut – a round brilliant cut diamond – as an example. Here’s how to talk about diamonds like a pro!
Table: The ‘table’ of a diamond is its top flat facet, which is also the facet with the largest surface area. The table size and its ratio to the girdle diameter is important, as this facet determines the amount of light rays entering the diamond and thus affects the refraction and appearance of the diamond.
Girdle: A diamond’s ‘girdle’ is its middle, widest portion, which is also the section with the largest diameter. The girdle is also the most fragile part of a diamond, which is why the ‘girdle thickness’ is of considerable importance. A girdle that is extremely thin is known as a ‘knife edge’ and has a heightened risk of chipping and is more susceptible to damage. On the other hand, an overly thick girdle is also not desirable as it unnecessarily addes weight to the gem where it matters the least, making it appear smaller.
GIA certified diamonds have a microscopic laser inscription of the GIA report number on the girdle which can only be viewed under a microscope. It is proof of the authenticity of a diamond.
Image credit: GIA.edu
Crown: The upper portion of a diamond above the girdle is aptly named the ‘crown’. The crown height and crown angle (which is the angle formed where the bezel facet meets the girdle) both affect the dispersion of light and brightness of the diamond.
Pavilion: The lower portion of a diamond from girdle down is called the ‘pavilion’. The pavilion depth bears significance as it affects a diamond’s brilliance. If the pavilion is too deep or too shallow, light could escape from the side of bottom of the gem more easily, whereas a well-cut diamond should be able to refract and direct more light back towards the surface of the diamond through the crown. The pavilion angle is also considered an important dimension for diamonds as it is related to the brightness of the stone.
Culet: At the bottom tip of a diamond is a small facet called the ‘culet’, which is intended to prevent abrasion and chipping to the point. Not all diamonds are cut to have a culet, and in that case, it is sometimes referred to as a ‘pointed culet’. An ideal culet should be invisible to the unaided eye.
After this introduction to a diamond’s anatomy, more will follow in our next blog, in which will share with you the ideal ratio and size of each part of a diamond that could contribute to an ‘Excellent’ grading. Laine Jewellery wishes you a warm and sparkling festive season with your loved ones🎄🎁. See you in 2022!
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