The decision to acquire diamonds can be both exciting and overwhelming. Understanding what makes a diamond valuable is key when choosing the right stones for your precious piece. Rest assured with basic knowledge you’ll be confident to make the right selection and ensure your fine jewellery is enjoyed for generations to come.

What is a diamond and how are they formed?

Hundreds of kilometres beneath the earth’s crust, under immense pressure and heat, crystallised carbon is formed, otherwise known as diamond. This mineral is brought to the earth’s surface in the process of molten rock cooling and expanding, creating channels for the diamond to travel through.

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What makes a diamond so valuable?

Diamonds are an incredibly hard material and gem-quality diamonds are rare and precious. Only 25% of diamonds mined each year are suitable for jewellery with the rest being classified as industrial grade. Diamonds are a natural product; each diamond is truly unique. Just as humans can be identified by fingerprints and DNA, diamonds have different characteristics which will affect their value. These characteristics are measured by the 4 C’s, considered to be the global language of diamond quality and used to determine why one diamond is more expensive than another. When shopping for a diamond, it is important to have a basic understanding of this principle so you can decide on the best diamond for you. Gem quality diamonds in their natural state are called rough diamonds. The rough diamond is sent to highly skilled diamond cutters to shape and polish them to perfection. The work done by these craftsmen is an art and the quality of their job significantly impacts the beauty and value of the diamond.

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What do the 4 C’s stand for?

A diamonds beauty and quality is determined by a combination of factors, commonly known as the 4 Cs - Cut, Clarity, Colour and Carat. When selecting diamonds, it’s a fine line to balance the factors that are most important to you, ensuring you make a decision that satisfies both your heart and your budget.


The beauty of a diamond depends on the way it interacts with light. You want your diamond to light up the room so make sure the diamond you select is well cut. The magnificent display of light you see is made up by brightness (reflection of white light from the surface and interior of the diamond), scintillation (pattern of light and dark, and the sparkle you see) and fire (flares of colour emitted from a diamond). A diamond’s light performance is measured by 3 factors; proportion (how the diamonds angles and facets relate to one another), symmetry (the precision of its cut) and polish (the condition of your diamonds surface). Each of the three factors are rated and then described as excellent, very good, good, fair and poor.

There are 5 basic sections to a diamond.

  1. The table - the flat surface on the top of the diamond
  2. The crown - the section of facets between the table and the girdle of the diamond
  3. The girdle - the horizontal midsection and widest part of the diamond
  4. The pavilion - the section of facets between the girdle and the bottom tip of the diamond
  5. The cutlet - the bottom tip of the stone
A traditional round brilliant diamond consists of 58 facets: 33 in the crown and 25 in the pavilion. A well-proportioned and symmetrical diamond will allow light to enter and exit through the crown.

Many jewellers refer to the shape of a diamond when discussing it’s cut. There are many shapes available with the most popular being round, but don’t be afraid to explore other options in your search for the perfect diamond here at Offe’s.

The flaws found in a diamond are referred to as inclusions or blemishes. These tiny imperfections may be crystals of foreign matter, another diamond crystal, or structural imperfections that can appear whitish or cloudy. The clarity grade awarded to a diamond is based on the number, size, type, position and visibility of these inclusions.

Under the industry standard of x10 magnification, the clarity of a diamond is rated according to the following scale from best to worst:

  1. Flawless – No inclusions or blemishes are noticeable under magnification
  2. Internally Flawless – No inclusions, blemishes only visible under magnification
  3. Very, Very Slightly Included (VVS) – Inclusions that are difficult to see under magnification
  4. Very Slightly Included (VS) – Minor inclusions that are somewhat easy to see under magnification
  5. Slightly Included (SI) – Inclusions that are noticeable under magnification
  6. Included (I) – Inclusions and or blemishes that are easily visible to the naked eye
A truly flawless diamond is incredibly rare and extremely expensive making up a very small percentage of the world’s diamond stocks. Almost every diamond has inclusions and remember they are mostly seen under x10 magnification. Inclusions and blemishes will have an effect on price if they’re large in size and situated near the centre of the diamond. Look for a diamond with inclusions that are smaller and situated round the edges.

When looking for a diamond (aside from fancy coloured diamonds like pinks), the best colour diamond is one with no colour at all. Even the slightest of hues can make a dramatic difference to a diamond’s value. Chemical impurities and structural defects affect the diamond’s colour and only a chemically pure and structurally perfect diamond is completely transparent and colourless. Diamonds are colour graded on a scale from D (colourless) - Z (dark yellow). D colour diamonds are very rare so relatively expensive. As you move down the scale toward a H/I colour you will find a diamond that still appears white to the human eye, but is more common, therefore more affordable. Fancy colour diamonds, with deep yellow, pink or other significant colour, have become especially prized in recent times and are rated on a different scale. When thee fancy coloured diamonds occur naturally, they are rare and expensive.

The size or weight of a diamond is measured in carats which are then measured in increments called points. One carat equals 100 points. Carat is the easiest of the 4 C’s to determine by weighing the stone on a set of diamond scales. The value of a diamond will increase in relation to carat weight. It’s important for you not to base your diamond choice on carat or size alone, remember to consider the other 3 C’s. For example, you may choose a particular diamond because it weighs 1 carat. However if this diamond does not have a good cut it’s appearance will reflect a much smaller stone.

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What should I know about Diamond Certificate?

Some diamonds, purchased loose or already set in jewellery, will come with a Diamond Certificate. This report, prepared by an independent diamond grader, is based on an evaluation of the individual diamond’s 4 C’s and can also be known as a Diamond Grading Report, or Diamond Dossier. These documents give you important information to help you make an informed purchase. They are particularly important if you don’t have a close and trustworthy relationship with your jeweller. At Offe Jewellers, we’ll invest personal care and time to understand your diamond requirements before helping you select the best stone for you. Rest assured, our expert, in-house gemmologists will source diamonds for you to view with independent documentation.

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Who can I trust to deliver a trustworthy Diamond Certificate?

Gemmological Institute of America (GIA) is the world’s most widely used lab and their certificates are considered the hallmark for integrity in the diamond world. In the 1940’s GIA developed a consistent way to describe a diamond in common language and their mission is to “protect all buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality.”

There are 2 types of reports supplied by the GIA;

  • The GIA Diamond Grading Report, which provides scientifically determined information on shape clarity, colour, cut, carat weight, proportions, finish and treatments. It includes a diagram of the diamond showing any inclusions that affect the clarity.
  • The GIA Diamond Dossier is a more concise version of the full report.

The International Gemmological Institute (IGI) was established in 1975 and is the largest, independent grading and appraisal organisation, with headquarters in Antwerp and offices around the world, including New York, Bangkok, Mumbai, Tokyo and Dubai. At IGI several gemmologists carefully analyse each diamond to produce an accurate description of its characteristics in relation to the 4 C’s. This information is stored on a database so you can request copies of your report if required. IGI also offers coloured gemstone certificates, educational courses and laser inscription services.

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