Jun 23

Understanding Gemstone Sizes

You may have heard of carat as the most popular term used to describe the size of a gemstone. However, depending on the shape and type of gemstone, its size can be expressed in different terms such as millimetres. If the gemstone is round then two dimensions are taken into consideration when talking about size, depth and diameter. If it has an oval or fancy shape, then its size is described in terms of width, length and depth. No matter what the dimensions used to describe size, it’s important to keep in mind that big is not always better, and depending on the stone, sacrifices have to be made.


Let’s take a look at the ways used to describe gemstone size:


Carat weight: The weight of a gemstone is mentioned in ‘carat’. It is not a good measure of the size of a gemstone. Carat weight is sufficient to describe size only when talking about diamonds, as they are always cut with a certain tolerance and are usually have a diameter of 6-6.1 millimetres.


Length, width and depth: The unit of measurement internationally recognised when talking about the size of gemstones and jewellery is millimetres. This is applicable for diamonds as well as coloured stones. While diamonds generally have a diameter of 6-6.1 millimetres, other stones might range from 5 – 8 millimetres. This depends on the specific gravity and density of the gemstone. This is the reason it is important to mention millimetres needed when ordering casting of coloured stones. A one-carat fire opal will be oversized for a ring mounting designed for a one carat round diamond, while a one-carat round cubic zirconia will be small.


When considering the size of gemstones it is best to consult a reliable jeweller and ask them to guide you through the selection process. 

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