Diamonds are among the rarest and most valuable of all gemstones. Diamonds with natural colour are even rarer, making up only 0.01% of the world’s total diamond production.

Fancy Coloured Diamonds

“Fancy” is a term GIA uses for grading coloured diamonds, with Fancy Intense, Fancy Deep, and Fancy Vivid having the strongest colour and considered to have the greatest value.

Fancy coloured diamonds are extremely rare in general, and the most common naturally-occurring coloured diamonds are typically the canary yellow diamond.

Recently, there has been a huge demand for fancy blue diamonds, including the De Beers Millennium Jewel 4 and the Shirley Temple Blue diamonds that have recently been setting records at auctions.

While these coloured diamonds are increasingly popular, there is one colour in particular that is rarer than all the rest …

Fancy Red Diamonds

Red diamonds are extremely rare and astronomically expensive. Only a small handful of predominantly red (meaning that red is the primary colour with no secondary hues, like purple or brown) diamonds have ever been documented.

According to the GIA, red diamonds are so rare that their records show that over a 30 year period from 1957 to 1987 there was not a single mention of a grading lab report issued for a diamond with “red” as the only descriptive term.

The largest known red diamond in the world is the Moussaieff Red Diamond – and it’s only 5.11 carats.

Red Diamonds - Moussaieff Red Diamond

What makes them red?

In short – we’re still sort of figuring that out.

Researchers that have studied diamonds for decades are still not exactly sure what causes their unique colour. One explanation is that “defects in the atomic structure that result from gliding (the slight movement of atoms along the octahedral direction) are partially responsible.”

Both natural and synthetic diamonds can be treated to produce a red color, usually with irradiation followed by annealing or a coating.

Where do red diamonds come from?

For most of human history, these diamonds were only found very sporadically in India, Brazil, Indonesia, and southern Africa. That all changed with the opening of the Argyle diamond mine in Western Australia in 1985.

The Argyle mine is the only known significant source of pink and red diamonds, producing over 90% of global supply. The mine also producers a lot of other naturally coloured diamonds, including champagne, cognac and rare blue diamonds.

The Argyle mine continues to be the world’s largest source of pink coloured diamonds. These diamonds are graded into specific sub-categories of colour including purplish pink, orangy pink, brownish red, brown-pink, pink-purple and other somewhat funny-sounding colour distinctions. These also include the straightforward “pink” and “red” colour grades. Of all the pink-hued diamonds that have been sold from Argyle since 1985, only 1% of the stones were graded as having a distinctly red colour.

With the Argyle mine set to close around the year 2020, the future supply of pink and red diamonds looks uncertain.

How expensive are red diamonds?

Very, very expensive.

For example, let’s look at a regular 1 carat round brilliant diamond. Depending on a wide variety of factors, you’d be looking at a price of $3,000 and $25,000 per carat.

For red diamonds, some will go for $400,000 per carat, or even $1,000,000 per carat like the famous 0.95 ct Hancock Red Diamond that broke auction records back in 1987.

Read more about diamonds, or learn about the 4 Cs of diamond quality.