Education

Coloured diamonds: a collector's guide.

Emeralds. Rubies. Sapphires. And now, coloured diamonds—the new standard in gemstone investment.

Selection of coloured gemstones in varied hues
01

The 4Cs

Fancy coloured diamonds are graded by the 4Cs, but with a different order of priority. Colour is paramount—its hue, tone, and saturation define rarity and value, with Fancy Vivid being the most sought-after grade. Clarity is less critical, as inclusions are often concealed by the stone's colour intensity. Cut is judged not by brilliance but by how effectively it enhances and distributes the natural colour. Carat weight adds value, but a smaller stone with exceptional colour will always command a higher premium than a larger stone with weaker hue.
  • Colour — hue, tone, saturation—Fancy Vivid is the top grade
  • Carat — adds value, but colour intensity outranks size
  • Cut — enhances and distributes colour, not brilliance
  • Clarity — less critical—colour often hides inclusions
What this means when you buy

We evaluate every stone we purchase and sell according to these rigorous criteria. And while video offers a useful preview, we strongly recommend viewing the stone in person—only then can its true colour, clarity, and character be fully appreciated.

Are colour diamonds a good investment?

Yes, due to growing demand and shrinking supply. Coloured diamonds combine extreme rarity, proven appreciation, portability, and beauty—making them one of the most compelling alternative investments available today. The rarest colours are red, green, orange and purple/violet, the second rarest would be pinks and blues.

02

Treatments

Diamond treatments are artificial processes used to enhance a stone's colour or clarity. Common treatments include laser drilling and fracture filling for clarity, and HPHT, irradiation, or coating for colour enhancement. While some treatments are permanent and stable, others require careful maintenance and may affect durability. Full disclosure is essential—not only for accurate valuation but also for long-term care and peace of mind. We always provide transparent information on any treatment, so you know exactly what you are acquiring.
  • Coatings — Diamonds are the most commonly encountered coated gemstones. Coating methods include permanent ink markers along the girdle—crude but effective—and more modern techniques using metal oxide thin films.
  • Fracture Filling — Surface-reaching fractures are sometimes filled with high-lead-content glass to reduce their visibility and enhance the diamond's appearance. While the fracture remains present, the treatment renders it far less apparent to the naked eye.
  • High pressure, high temperature (HPHT) treatment — High-pressure, high-temperature (HPHT) treatment can remove or reduce brownish coloration, producing a colourless diamond. The same process can also transform brown diamonds into yellow, orangy yellow, yellowish green, or blue.
  • Irradiation — Neutron and electron irradiation are the most common forms of artificial diamond colouring. These techniques can produce black, green, blue-green, deep yellow, orange, pink, and red diamonds—often with a secondary heating step to achieve or stabilize the desired colour.
  • Laser Drilling — Laser drilling uses a focused laser beam to burn a tiny channel from the diamond's surface to a dark inclusion. A chemical is then introduced through the channel to dissolve or alter the inclusion's appearance. This treatment is unique to diamonds—only they can withstand the intense heat of the laser.
What this means when you buy

We don't recommend collectors/buyers to purchase colour diamonds that are already set in jewellery.

Should I consider a rare colour but treated diamond with report for purchase?

Absolutely not, unless it's just for fun and very well priced.

03

Colour

The colours of natural fancy diamonds are born from unique conditions deep within the earth. Nitrogen impurities produce yellow and orange hues; boron creates blue diamonds; lattice distortion—a twisting of the crystal structure—gives rise to pink, red, and purple; and natural radiation colours diamonds green. Each colour tells a distinct geological story, and these variations in origin directly influence rarity, desirability, and investment value.
  • Orange — Nitrogen + lattice defects (Very rare)
  • Red — Extreme lattice distortion (Extremely rare)
  • Blue — Boron (Very rare)
  • Purple — Lattice distortion + hydrogen (Extremely rare)
  • Green — Natural radiation (Very rare)
  • Yellow — Nitrogen (Common)
What this means when you buy

Colour plays a major role in price determination according to the rarity, however the other factors needs to be considered as well when it comes to purchasing.

What does it mean when a combination of colour written on the report?

It means the body colour of the diamond displays two or more tones with the last colour written being the dominate one. The modifiers are listed before the primary colour.

04

Report

A coloured diamond report—most commonly issued by the GIA—is the definitive document that certifies a diamond's colour, origin, quality, and authenticity. It evaluates the stone's hue, tone, and saturation, assigning a fancy colour grade from Faint to Fancy Vivid, and also records carat weight, clarity, cut, and any treatments. This report is the internationally recognized standard for valuation and transparency—essential for buyers, collectors, and investors seeking confidence in their acquisition.
  • Colour Grade — The stone's hue, tone, and saturation—e.g., Fancy Intense Pink
  • Origin of Colour — Natural or treated?
  • Carat Weight — The stone's weight
  • Clarity Grade — Presence of inclusions—secondary to colour
  • Cut Quality — How well the cut enhances colour
  • Inscriptions — Laser-inscribed GIA number on the diamond
  • Additional Comments — Clarity plot, treatment details, special features
  • Security Features — Hologram, microprinting, QR code, unique report number
What this means when you buy

It's important to renew/update the report before purchase by a third party and not the seller.

Should I purchase a stone with no report or a non GIA report?

No, we would not recommend you to do that unless you are a trader and have the years of experience and skills of buying and selling.

Frequently asked

Questions collectors ask us most often.

Which rare stones does Gem Solutions source?

We can source any stone according to the client's requirements and budget.

Do coloured diamonds use the same labs as coloured stones?

Coloured diamonds are graded principally by GIA on the Fancy colour scale. Coloured stones go to the gem laboratories — Gübelin, SSEF, GRS, AGL. We route each stone to the laboratory its market expects.