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Why Do Diamonds That Look Similar Have Different Price Tags?

“I’m really confused,” Rob told me. “I found two diamond rings I thought my girlfriend would really like. They looked really similar, but had a price difference of £5,000. “I can’t understand why! How do I pick between them?” Rob came to us after becoming concerned that he did not understand enough about diamonds to make an informed, confident decision about which engagement ring to buy for his girlfriend.
In fact, we hear the same anxiety from many new customers. It is undoubtedly difficult and frustrating to make such a big decision without all the information you need in front of you. We explain that the price of a diamond depends on how rare and how perfect it is. Diamonds are graded according to four factors, known as the 4 C’s.


This is the measurement of how much a diamond weighs. It’s not quite the same as their size, because two diamonds of equal carat weight may appear very different in size, based on their shape. In addition, two diamonds of equal carat weight can have very different costs, based on the three other factors…


This refers to the amount of flaws (blemishes and inclusions) that are found within the stone, which can be seen under a magnifying glass. Unsurprisingly, diamonds with no or few inclusions and blemishes are more highly-valued and priced. While flawless diamonds are the rarest and most expensive, a diamond does not have to be flawless to be stunning, and there are a few different grades to choose from. If your stone weighs over a carat, you will receive a GIA certificate with your stone that includes a “plot” of the diamond’s inclusions. (Under a carat, you get a simplified version of this certificate, called a dossier.) As no two diamonds are exactly the same, comparing the uniqueness of your diamond’s clarity characteristics with the plot provided offers assurance that the diamond you pay for is genuine and authentic.


This relates to how colourless or “white” a stone is. Diamond colour is graded according to the GIA colour scale, from D to Z, where D is rated as the most colourless, and thus, the most rare and expensive.


The cut of the diamond determines its brilliance, so the better cut the diamond, the more sparkly it will be. The cut will also determine the shape. Round is perhaps the most common, but other popular ones include oval, emerald, cushion, marquise, pear and princess. The price will be determined according to the balance of these factors, which will be noted on the diamond’s certificate. But wait…. There’s more. Two diamonds might have very similar descriptions on their certificate, in terms of the 4 C’s, and yet still be valued differently. For example, not all diamond flaws are created equal. Some might be more noticeable to the naked eye, internal rather than external, or more serious. They need to be properly examined with a lens in order to tell. Others might be clean, well-made stones technically, but appear slightly milky, lacking the lustre and full life a good diamond should have. This can be a little more subjective – and is where a diamond expert like Sterling Diamonds comes in.
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