Carat is the unit of measurement for a diamond's weight. One carat is equivalent to 200 milligrams. Larger diamonds generally have a higher carat weight and are often considered more valuable. However, other factors, such as cut, colour, and clarity, also play a significant role in determining a diamond's overall quality and value.
Diamond polish refers to the quality of the surface finish of a diamond, evaluating the smoothness and precision of its facets. Graded on a scale ranging from Excellent to Poor, with several intermediate categories like Very Good and Good, the polish grade directly influences a diamond's brilliance and overall visual appeal. A higher polish grade indicates that the diamond's facets have been meticulously polished to minimize any microscopic imperfections on the surface. This results in enhanced light reflection and refraction within the diamond, allowing for optimal sparkle and fire.
Jewellery Services recommends excellent and very good polish grades.
The cut of a diamond refers to how well the diamond has been shaped and faceted. It is not about the diamond's shape (round, princess, etc.) but rather about how well it reflects light. The quality of the cut affects the diamond's brilliance and sparkle. The GIA grades diamond cuts on a scale ranging from Excellent to Poor.
Diamond symmetry refers to the precision and alignment of the diamond's facets, as well as the balanced arrangement of its various components. Graded on a scale from Excellent to Poor, symmetry is an important factor in assessing the overall quality of a diamond's cut. A diamond with excellent symmetry reflects light in a consistent and uniform manner, contributing to its brilliance and sparkle. In contrast, poor symmetry can result in uneven light distribution, affecting the diamond's overall appearance.
Jewellery Services recommends excellent and very good symmetry grades.
Diamond colour refers to the presence or absence of colour in a white diamond. The GIA colour scale ranges from D (colourless) to Z (light yellow or brown). The most valuable diamonds are usually colourless or near-colourless, as these diamonds allow more light to pass through, resulting in greater brilliance.
The diamond table percentage refers to the size of the flat, topmost facet of a diamond in relation to the overall diameter of the diamond. The table percentage is a critical factor in assessing a diamond's cut quality. It is calculated by dividing the width of the table facet by the average diameter of the diamond and multiplying by 100 to express the result as a percentage.
Clarity is a measure of the presence of internal and external flaws, known as inclusions and blemishes, respectively. The GIA grades clarity on a scale from Flawless (no inclusions or blemishes visible under 10x magnification) to Included (inclusions and/or blemishes visible to the naked eye). The fewer the inclusions and blemishes, the higher the clarity grade and the more valuable the diamond.
The diamond depth percentage is a measure of how deep the diamond is relative to its diameter. It is an important factor in assessing the overall cut quality of a diamond.
The depth percentage, along with other factors such as table percentage, crown angle, and pavilion angle, contributes to the diamond's cut grade. A well-proportioned depth percentage ensures that light entering the diamond reflects and refracts properly, resulting in optimal brilliance and fire. If the diamond is too shallow, light may leak out from the bottom, leading to a lack of sparkle.
Conversely, if the diamond is too deep, light may escape through the sides, also diminishing its brilliance.
Diamond fluorescence refers to the phenomenon where a diamond emits visible light when exposed to ultraviolet (UV) light. This fluorescence is typically blue in colour, but diamonds can also fluoresce in other colours such as yellow, green, or white. The presence and strength of fluorescence are graded on a scale from None to Very Strong.
While some people appreciate the unique glow that fluorescence can impart to a diamond, excessive fluorescence, especially in blue, can sometimes lead to a milky or hazy appearance in certain lighting conditions.
Jewellery Services recommends none to faint fluorescence grades.
The diamond ratio refers to the relationship between the width and length of a diamond, and it is calculated by dividing the length of the diamond by its width. The resulting ratio is an important aspect of a diamond's shape and overall appearance. Different diamond shapes, such as round, princess, oval, or emerald, have different ideal ratios that are considered more visually appealing. For round brilliant diamonds, which are the most popular shape, the ideal ratio is 1.0, meaning the diamond is perfectly round.
GIA - The Gemological Institute of America (GIA) was established in 1931 and is one of the world’s foremost authorities on diamonds, coloured stones, and pearls. A public benefit, nonprofit institute, the GIA is a leading source of knowledge, standards, and education in gems and jewellery.
IGI - The International Gemological Institute (IGI) is the world’s largest gemological institute with 29 laboratories and 18 schools in 10 countries, the IGI has a workforce of over 1,000 experts dedicated to industry service and consumer protection.
