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?

Diamond Color, Clarity, Cut and Carat Weight are collectively termed the 4Cs – the factors that, when combined, define a diamond’s quality and ultimately determine its value. The Gemmological Association of America (GIA) created the 4Cs of Diamond Quality, which has become the universal method for assessing the quality of any diamond, anywhere in the world.

The creation of the 4Cs means that diamond quality can be communicated in a universal language so diamond purchasers know
exactly what they are buying.

GIA’s diamond colour grading system measures the absence of colour, starting with D as colourless and continuing to Z representing light yellow or brown. The distinctions between colour grades are so subtle that they are often invisible to the untrained eye but can make a big difference in diamond quality and price.

This video produced by the GIA further explains diamond colour.


Natural diamonds form from carbon exposed to tremendous heat and pressure deep in the earth. Diamonds often contain clarity characteristics, called inclusions or blemishes. Inclusions are enclosed within the gem and blemishes are on the surface of the diamond. If all else is equal, the closer a diamond is to flawless, with no inclusions or blemishes, the higher its value.

This video produced by the GIA further explains diamond clarity. 



A diamond’s cut determines its sparkle. To fashion a stone with proportions, symmetry and polish worthy of an excellent cut grade requires artistry and workmanship. The finer the cut quality, the more sparkle the diamond has.

This video produced by the GIA further explains diamond cut.



Diamond weight is measured in carats. One carat is equal to 0.2 gram, about as heavy as a paperclip. Since larger diamonds are more rare, they will cost more than a smaller gem with the same colour, clarity and cut grades.

This video produced by the GIA further explains diamond carat weight.


What should I know about Diamond Certificates?

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. At Offe Jewellers, our expert, in-house gemmologist and diamond graders will invest personal care and time to understand your diamond requirements before sourcing the stone best suited to you. 

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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 the 4C's, 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 diamond quality.”


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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