Loose diamonds

Everything you need to know about natural diamonds, guided by Royal Coster Diamonds

Since Royal Coster Diamonds has one of the largest collections of loose diamonds in Europe, we can say there is a stone that fits your wishes and personal style. To help you make the right choice, we offer a clear and accessible guide that explains the 4C’s of diamonds. Understanding cut, color, clarity, and carat weight is essential when selecting a diamond, as each element influences its appearance and value in a different way.

One of Europe’s most extensive selections of natural loose diamonds

What you see online is just a small part of what we offer. In our Boutique on Museumplein, you will find one of the largest selections of natural loose diamonds in Europe.

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The 4C's

A diamond is graded by the 4C's. Together they determine the value of a diamond. 

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The Certificate: the fifth C that truly matters

Carat, color, clarity, and cut. These are the so-called 4 C's. You take them into account you're about to make one of the most important purchases of your life. But before you start dreaming about that sparkling beauty, let's talk about another Big C. The Certificate. A diamond certificate is your guarantee of quality, authenticity, and transparency, giving you confidence in one of life’s most meaningful purchases.

How does a diamond get certified?

With various high-powered microscopes in special laboratories. Professional gemologists use them to measure and study the diamond's symmetry, color, size and shape. They also pay great attention to certain flaws and the quality of the cut. Once the gemologists determined all the different properties, they attach a report to the diamond. The report holds an accurate description of the examination. Sometimes, the gemologists use high-level heat or lasers to improve certain properties of the diamond. Trustworthy agencies put these enhancements on the report as well to inform the buyer about the “upgrade”.

The certification standards of Royal Coster Diamonds

At Royal Coster Diamonds, every diamond is certified by an independent and internationally recognized grading institute. We work exclusively with leading authorities such as:

  • Gemological Institute of America (GIA)
  • International Gemological Institute (IGI)
  • Diamond High Council (HRD)

These institutes are known worldwide for their strict grading standards, consistency, and transparency. Their certificates provide a detailed and objective assessment of each diamond’s cut, color, clarity, and carat, ensuring that every stone meets the highest international benchmarks. By working only with these trusted organizations, Royal Coster Diamonds offers complete confidence in the quality and authenticity of every diamond.

Royal Coster Diamonds works exclusively with ethically sourced natural diamonds

At Royal Coster Diamonds, certification goes hand in hand with responsibility. We work exclusively with ethically sourced, natural diamonds from verified and conflict free origins. Through our collaboration with the world’s leading certification institutes – GIA, IGI, and HRD – we ensure that each diamond’s origin, quality, and authenticity are fully traceable and verifiable.

Our mission is to unite the timeless art of diamond cutting with the values of today: sustainability, transparency, and respect for people and the planet. In doing so, we contribute to a future where luxury and ethics go hand in hand.


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