In co-operation with Dediam GL-Koru guarantees that the diamonds we sell are high quality and ethically produced. Because our diamonds come without intermediaries directly from the diamond exchange both price and quality are absolutely correct. From 0.3-carat diamonds an independent certified quality certificate of the Qualitative Diamond Classification Laboratory (e.g. GIA) is included automatically.

Dediam - Expert Diamond Manufacturer & Dealer

From more than 60 years of experience within the diamond industry Dediam holds a strong position in the Diamond Market.

The story of the Dediam company started several decades ago in the town of Amsterdam, when the trade of diamonds was concentrated there. The early founders traded rough and polished diamonds. They also cut their diamonds locally. When the diamond trade moved to Antwerp, it was a logical move to follow. In Antwerp they continued their cutting facilities and the trade of rough and polished diamonds. Today the knowledge of the trade has been passed on to a sixth generation, and the company keeps its position as market player on the Antwerp Diamond Market.

Because Dediam has been many years in business, the company has established its name in the diamond world and is well connected within the industry. As a strong-values family company, the dediam-team is proud they know 98% of all their customers personally. Long lasting personal connections is one of its core values for all collaboration, may it be on the supplier or customer side of business.

How to Choose a Diamond

There are four key factors to consider when choosing a diamond.

4Cs — cut, carat weight, color and clarity


Cut is the most important factor, which creates that breathtaking brilliance.


Carat Weight

“Carat” denotes the weight of a diamond (1-Carat = 0,2 g). Taken by itself, carat does not determine a diamond’s value. Two diamonds of equal weight can vary widely in price. 


Each stone is color-graded to a precise scale from “D” (colorless) to “Z” (saturated).


A stone is graded as flawless if, under 10-power magnification, no internal flaws are visible. Absolutely flawless diamonds are exceedingly rare and priced accordingly.

 Special Shapes and Colors

 We proudly deliver single stones, matching pairs or lines in special shapes:

Oval, Pear shape, Marquise shape, Princess cut, Flanders cut, etc.

When in need of colors, we have a choice between natural treated diamonds

(blue, green, yellow, cognac, pink and black)

as well as natural colors (brown, pink, blue, orange, green, etc).

You are welcome to visit us in order to discuss the different cuts in gemstones and how they can enhance your jewellery.


GL-Koru Oy

Kalevankatu 9  00100 Helsinki

+358 50 345 46 48

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Website development: Irene Sema

Photography: Irene Sema,  Vili Englund