Wishlist
Shopping Bag:
0845 680 6848 
The Four Cs
The ‘4Cs’ are the four key characteristics of diamonds: carat, cut, colour and clarity. The 4Cs provide the information needed to compare the characteristics of different diamonds. View all Diamond Jewellery and Bridal Jewelleryat Astley Clarke.
Diamond characteristic number one – Carat
The size of a diamond is measured in carat weight. One carat is equivalent to a fifth of a gram, or exactly 200 milligrams. Each diamond carat is also equal to 100 points; therefore a diamond that is a 1/2 carat can also be referred to as a 50-point diamond. The value of a diamond increases exponentially in relation to carat-weight, with sharp jumps around milestone carat weights, so that a 1.05-carat diamond will be significantly more expensive than a comparable 0.95-carat stone. Poorer quality diamonds tend to be cut to increase their carat-weight and therefore their price, but will not in fact have as much brilliance as a better-cut, lower carat diamond. Carats are also used to measure gemstones other than diamonds.
Total carat weight (t.c.w.) is a phrase used to describe the total mass of diamonds and other stones in a piece of fine jewellery, where more than one gemstone is used. Diamond solitaire earrings, like the Flora Astor ones in the Astley Clarke range, for example, are quoted in t.c.w, indicating the mass of the gemstones in both earrings.
To create a single, one-carat diamond, on average nearly 250 tons of ore must be mined – this explains part of the reason why diamonds are so treasured and expensive.
Diamond characteristic number two – Cut
The shape of a diamond is commonly confused with the cut, but the two are in fact distinct. The cut refers to the number and angles of the facets. This determines how much light a diamond reflects. A diamond-cutter always attempts to cut a diamond to make the best use of light. When a diamond is well-cut, light is refracted successfully from one facet to another and dispersed through the top of the diamond. If it is cut too deep, some light escapes through the opposite side of the diamond, while if it is cut too shallow, light escapes through the bottom of the stone before it can be reflected. A well-cut diamond has the greatest brilliance, scintillation and fire and therefore looks the most attractive.
The technique for cutting diamonds have been developed over hundreds of years, with the greatest innovations made in 1919 by the mathematician and gem enthusiast Marcel Tolkowsky. He developed the round brilliant cut by calculating the exact shape which return and scatter the most light when the diamond is viewed from above. A diamond cut to his specifications has 57 facets (polished faces), with 33 on the crown (the top half) and 24 on the pavilion (the lower half).
New diamond cuts are constantly being invented. One introduced in 2003 is called the Genesis cut and features concave surfaces and angles, and resembles a 4-pointed star.
Diamond characteristic number three – Colour
This is the natural body colour visible in a diamond and is the one C determined completely by nature, not by man. Generally speaking, the closer a diamond is to being totally colourless, and therefore chemically pure and structurally perfect, the more valuable and beautiful it is. The most common impurity found in diamonds is nitrogen – this replaces a small proportion of carbon atoms in a diamond’s structure and causes a yellowish to brownish tint. This effect is present in almost all white diamonds, and finding one in which this is undetectable is extremely rare. In the colour grading system used for diamonds, the colour grades D, E and F are considered colourless and are the rarest and most expensive of diamonds.
Coloured diamonds, known as ‘fancy diamonds’ are even rarer than perfectly colourless diamonds and extremely expensive. These colours include pink, yellow, blue, brown, orange, black and green.
Diamond characteristic number four – Clarity
Clarity is an indication of the purity of a diamond. When a rough stone is extracted from carbon, deep beneath the earth, tiny traces of natural elements, usually non-crystallised carbon, are almost always trapped inside. Further, there are often structural imperfections such as tiny cracks, which can appear whitish or cloudy. These imperfections are called inclusions. Most inclusions are not visible to the naked eye, so a jeweler will use a magnifier, known as a loupe, to reveal a diamond’s inclusions. The number, size, colour, relative location and visibility of inclusions all affect the relative clarity of a diamond, and diamonds are increasingly rare and precious when they have higher clarity gradings. Only around 20% of all diamonds mined have a clarity rating high enough for the diamond to be appropriate for use as a gemstone, while the other 80% are relegated to industrial use. Of the top 20 percent used in fine jewellery, a significant proportion contains one or more visible inclusions. Most inclusions found in gem-quality diamonds do not affect the diamonds' performance or structural integrity, but large clouds can affect a diamond's ability to transmit and scatter light.
Diamonds are graded by the major societies on a scale ranging from flawless to imperfect.
Visit Astley Clarke's Diamond Jewellery and Bridal Jewellery Collections.
Diamond characteristic number one – Carat
The size of a diamond is measured in carat weight. One carat is equivalent to a fifth of a gram, or exactly 200 milligrams. Each diamond carat is also equal to 100 points; therefore a diamond that is a 1/2 carat can also be referred to as a 50-point diamond. The value of a diamond increases exponentially in relation to carat-weight, with sharp jumps around milestone carat weights, so that a 1.05-carat diamond will be significantly more expensive than a comparable 0.95-carat stone. Poorer quality diamonds tend to be cut to increase their carat-weight and therefore their price, but will not in fact have as much brilliance as a better-cut, lower carat diamond. Carats are also used to measure gemstones other than diamonds.
Total carat weight (t.c.w.) is a phrase used to describe the total mass of diamonds and other stones in a piece of fine jewellery, where more than one gemstone is used. Diamond solitaire earrings, like the Flora Astor ones in the Astley Clarke range, for example, are quoted in t.c.w, indicating the mass of the gemstones in both earrings.
To create a single, one-carat diamond, on average nearly 250 tons of ore must be mined – this explains part of the reason why diamonds are so treasured and expensive.
Diamond characteristic number two – Cut
The shape of a diamond is commonly confused with the cut, but the two are in fact distinct. The cut refers to the number and angles of the facets. This determines how much light a diamond reflects. A diamond-cutter always attempts to cut a diamond to make the best use of light. When a diamond is well-cut, light is refracted successfully from one facet to another and dispersed through the top of the diamond. If it is cut too deep, some light escapes through the opposite side of the diamond, while if it is cut too shallow, light escapes through the bottom of the stone before it can be reflected. A well-cut diamond has the greatest brilliance, scintillation and fire and therefore looks the most attractive.
The technique for cutting diamonds have been developed over hundreds of years, with the greatest innovations made in 1919 by the mathematician and gem enthusiast Marcel Tolkowsky. He developed the round brilliant cut by calculating the exact shape which return and scatter the most light when the diamond is viewed from above. A diamond cut to his specifications has 57 facets (polished faces), with 33 on the crown (the top half) and 24 on the pavilion (the lower half).
New diamond cuts are constantly being invented. One introduced in 2003 is called the Genesis cut and features concave surfaces and angles, and resembles a 4-pointed star.
Diamond characteristic number three – Colour
This is the natural body colour visible in a diamond and is the one C determined completely by nature, not by man. Generally speaking, the closer a diamond is to being totally colourless, and therefore chemically pure and structurally perfect, the more valuable and beautiful it is. The most common impurity found in diamonds is nitrogen – this replaces a small proportion of carbon atoms in a diamond’s structure and causes a yellowish to brownish tint. This effect is present in almost all white diamonds, and finding one in which this is undetectable is extremely rare. In the colour grading system used for diamonds, the colour grades D, E and F are considered colourless and are the rarest and most expensive of diamonds.
Coloured diamonds, known as ‘fancy diamonds’ are even rarer than perfectly colourless diamonds and extremely expensive. These colours include pink, yellow, blue, brown, orange, black and green.
Diamond characteristic number four – Clarity
Clarity is an indication of the purity of a diamond. When a rough stone is extracted from carbon, deep beneath the earth, tiny traces of natural elements, usually non-crystallised carbon, are almost always trapped inside. Further, there are often structural imperfections such as tiny cracks, which can appear whitish or cloudy. These imperfections are called inclusions. Most inclusions are not visible to the naked eye, so a jeweler will use a magnifier, known as a loupe, to reveal a diamond’s inclusions. The number, size, colour, relative location and visibility of inclusions all affect the relative clarity of a diamond, and diamonds are increasingly rare and precious when they have higher clarity gradings. Only around 20% of all diamonds mined have a clarity rating high enough for the diamond to be appropriate for use as a gemstone, while the other 80% are relegated to industrial use. Of the top 20 percent used in fine jewellery, a significant proportion contains one or more visible inclusions. Most inclusions found in gem-quality diamonds do not affect the diamonds' performance or structural integrity, but large clouds can affect a diamond's ability to transmit and scatter light.
Diamonds are graded by the major societies on a scale ranging from flawless to imperfect.
Visit Astley Clarke's Diamond Jewellery and Bridal Jewellery Collections.
