Rare Natural Diamond Colors: When Size, Color and Price Collide

When most people think of diamonds, they imagine icy, near-colorless stones. In reality, natural diamonds occur in almost every color of the rainbow – and a tiny fraction of them are so rare that they’ve become legends. Among these “fancy color” diamonds, red, blue, pink, green, violet and pure orange are at the top of the rarity scale.

In this article we’ll focus on three things:

1. Which colors are considered truly rare

2. The sizes of the most important stones discovered

3. The extraordinary prices they’ve reached at auction

1. What makes a color “rare”?

The GIA grades colored diamonds by hue, tone and saturation, giving designations like Fancy, Fancy Intense and Fancy Vivid. The more pure and vivid the color, the rarer and more valuable the stone tends to be.

Market and geological data agree on a clear rarity list:

• Red – the rarest known diamond color, with only a handful of stones known worldwide, most under 1 ct.

• Blue & Pink – extremely rare, with huge demand from collectors and investors.

• Green, Violet & Pure Orange – also very rare, especially in saturated, unmodified hues.

Because nature almost never produces large, clean stones with vivid color, size multiplies rarity: once you cross 5-10 carats in these colors, you’re already in “museum piece” territory.

2. Red diamonds – tiny stones, huge prices

Red diamonds get their color not from impurities, but from distortions in the crystal lattice – the same mechanism as pink diamonds, but more extreme. They are so scarce that most known stones weigh under 0.50 ct.

The most important example is:

• Moussaieff Red Diamond

  • Color: Fancy Red

  • Weight: 5.11 ct (largest known red diamond)

  • Discovery: Brazil, from a rough crystal of 13.9 ct found in 1989

  • Estimated value: around $20 million, placing it in the multi-million-per-carat category.

Because so few red diamonds exist at any size, a clean stone above 1 ct already commands an exceptional premium; at over 5 ct, the Moussaieff Red is effectively unique.

3. Pink diamonds – record-breaking carat weights

Pink diamonds became famous largely thanks to Australia’s Argyle mine, which produced the majority of the world’s supply until it closed in 2020. High-quality pinks above 1-2 ct are rare; above 10 ct they are trophy assets.

Two headline stones show how size and price scale together:

• CTF Pink Star (formerly Pink Star)

  • Weight: 59.60 ct, Fancy Vivid Pink, Internally Flawless

  • Origin: rough of 132.5 ct mined by De Beers in 1999, cut over two years

  • Price: sold in 2017 at Sotheby’s Hong Kong for $71.2 million – still the highest price ever paid for any diamond or jewel at auction.

  • Approximate price per carat: about $1.2 million/ct.

• Eden Rose

  • Weight: 10.2 ct, round brilliant, Fancy Intense pink, internally flawless

  • Estimate (Christie’s 2024 sale): $9-12 million (roughly $900k-$1.2m per carat).

These results show that once a pink diamond passes roughly 10 ct with vivid color and top clarity, the market begins to value it in the high six- to seven-figure range per carat.

4. Blue diamonds – boron, rarity and multi-million-per-carat prices

Blue diamonds owe their color to trace amounts of boron in the crystal structure.  They are geologically rare and historically associated with famous stones like the Hope Diamond.

Modern auction records highlight how size and saturation drive value:

• Oppenheimer Blue

  • Weight: 14.62 ct, Fancy Vivid Blue

  • Sale: Christie’s Geneva, 2016

  • Price: about $57.5-58 million, at the time a world record for any diamond.

  • Implied price per carat: roughly $4 million/ct.

• Blue Moon of Josephine

  • Weight: 12.03 ct, Fancy Vivid Blue, Internally Flawless

  • Sale: Sotheby’s Geneva, 2015

  • Price: about $48.5 million, a then-record price per carat for any diamond (around $4 million/ct).

Even smaller vivid blues of 5-10 ct routinely sell for tens of millions, illustrating how quickly value accelerates once color, clarity and size align.

5. Green, violet and orange – rare hues, usually modest sizes

Other rare colors appear much less often and generally in smaller sizes:

• Green diamonds get their color from exposure to natural radiation over millions of years. High-saturation greens are scarce, and stones above a few carats with pure green color are extremely unusual.

• Violet and purple diamonds (often from Australia) are also rare; even sub-carat stones with strong color are prized.

• Pure orange diamonds (without brown or yellow modifiers) are among the rarest hues on the market; most are under 2-3 ct.

While individual auction records for these colors are less publicized than those for blue and pink, price-per-carat for vivid stones can reach similar levels once you combine strong color with even modest size.

6. How size and color interact in pricing

Across all fancy colors, three factors drive value:

1. Hue & saturation – “Fancy Vivid” or “Fancy Intense” commands a major premium over “Fancy” or “Fancy Light.”

2. Size (carat weight) – most natural color diamonds are small. Stones above 5 ct with top color are already rare; at 10 ct, they are almost unique; beyond 20-30 ct, they become world-class trophy pieces.

3. Clarity & cut – internally flawless or very slightly included stones, well-cut to maximize color, bring the very highest prices.

To see how size multiplies value:

• A 5.11 ct red diamond (Moussaieff Red) is valued near $20m, while most red diamonds under 1 ct already command high six-figure prices.

• A 12.03 ct vivid blue (Blue Moon of Josephine) sold for about $48.5m, ~$4m/ct.

• A 59.60 ct vivid pink (CTF Pink Star) fetched $71.2m, even with a lower price per carat than the blues, simply because it is so large and unique.

In other words, carat weight doesn’t just add value linearly. Once you reach sizes that exist in single digits worldwide for a given color and quality, the stone stops being priced like a normal gemstone and starts being treated like a one-of-a-kind artwork.

7. Takeaways for collectors and professionals

• Red, vivid blue and vivid pink are the key colors at the absolute top of the rarity and price spectrum.

• Most high-end auction pieces in these colors sit between 5 and 20 carats; anything significantly larger is virtually unique.

• Price per carat in top stones ranges from hundreds of thousands to several million dollars, depending on the color and the stone’s story.

• As major sources like the Argyle mine have closed, truly fine pinks and some violets are expected to become even scarcer over time, which is already reflected in auction estimates.