Coloured diamonds

What determines a stone's value

The original DeLoire guide also presents coloured diamonds as an alternative to traditional investments. The value of an individual diamond depends chiefly on its colour and the origin of that colour, weight, clarity, cut and documentation.

A diamond is a tangible object that can easily be transported. That does not mean it will command the same selling price everywhere: this depends on the buyer, market and selling costs. Setting it in an original piece of jewellery gives it a new form, not a guarantee of investment returns.

Naturally coloured red, green or blue diamonds can be exceptionally rare. Before choosing, it makes sense to assess the individual stone, not just the name of its colour.

How their colour is formed

The colour of natural diamonds relates to their composition and crystal structure. Nitrogen, for example, can produce yellow colour, and boron blue. Distortion of the crystal lattice plays a role in most pink diamonds and in red shades.

Green colouring may be associated with natural irradiation. Laboratory treatments can also alter colour, so it is important to know whether it is natural or treated. This is assessed by gemmological examination.

Coloured diamond shades

Brown, champagne and black — this group can offer more accessible stones, sometimes less expensive than a comparable colourless diamond. The individual quality and colour origin are decisive.

Yellow and orange — from subtle tones to striking Fancy Vivid shades. Intensity, saturation and the rarity of a specific colour strongly influence its assessment.

Argyle pinks — stones from Australia's Argyle mine form a distinctive chapter for collectors. The mine stopped production in 2020. It is not, however, the world's only source of pink diamonds.

Blue and green — rare natural colours for which evidence of colour origin is especially important. Blue can be associated with boron; green with irradiation under natural conditions.

Red — among the rarest coloured diamonds. Their colour relates to an unusual crystal lattice structure.

Investment also involves uncertainty

Prices can rise or fall, and resale may not be quick. Historical appreciation does not guarantee future returns or protection against inflation. When choosing, ask for an explanation of the documentation, total purchase cost and potential resale options.

Let's choose your stone in person

We will discuss colour, cut and budget, and whether the stone should remain loose or become part of a piece of jewellery. Radim develops a design around it, and Michaela takes you through the goldsmithing options.