The Most Expensive Diamonds in the World

Extraordinary Stones, Historic Prices, and Why True Rarity Has No Ceiling

Diamonds are often associated with romance and celebration, but at the very top of the market, they represent something more, something special, something enduring.

The world’s most expensive diamonds are not simply beautiful gemstones. They are geological miracles, created in the earth over billions of years, cut and shaped by expert hands and elevated by history. Their value extends far beyond a diamond’s typical carat weight or a grading report. Instead, it’s driven by rarity so extreme it may never naturally occur again, craftsmanship without compromise, and stories that span continents and centuries.

At MDT DESIGN, we believe the most compelling diamonds are those that combine technical excellence with meaning – the same philosophy that guides our approach to bespoke jewellery design and one-of-a-kind engagement rings.

What Makes a Diamond One of the Most Expensive in the World?

Before exploring the record holders, it’s worth understanding why some diamonds reach prices measured in tens of millions.

While the Four Cs, carat, colour, clarity, and cut, remain fundamental, the most valuable diamonds share more than these standard characteristics:

  • Extreme natural rarity, particularly in Fancy Vivid colours
  • Large size without quality compromise
  • Documented provenance, often linked to royalty or historic auctions
  • Market visibility, where elite collectors compete publicly

For those wanting a deeper understanding of how diamonds are assessed beyond headline prices, our Diamond Education resources explore the Four Cs and grading system in detail.

The Pink Star (CTF Pink Star)

The Most Expensive Diamond EVER Sold at Auction

  • Carat weight: 59.60ct
  • Shape: Oval mixed cut
  • Colour: Fancy Vivid Pink (FVP)
  • Clarity: Internally Flawless
  • Discovered: 1999
  • Sold: US $71.2 million (2017)
PINK STAR DIAMOND rare expensive and sizable, sat on someones hand.

The Pink Star diamond remains the modern benchmark for diamond rarity and value.

Originally discovered as a 132.5ct rough diamond, it took nearly two years of meticulous planning to cut the stone into its final form. The final result being a 59.60ct oval shape diamond with perfect pink colour saturation and exceptionally high clarity, a combination rarely ever seen at any size, let alone on this scale.

While diamonds of this rare size and colour are destined for museums or private collections, the same principles of proportion, symmetry, and cut quality apply when selecting a diamond for a handmade engagement ring.

The Oppenheimer Blue

A Defining Moment for Blue Diamonds

  • Carat weight: 14.62ct
  • Shape: Rectangular Emerald Cut
  • Colour: Fancy Vivid Blue (FVB)
  • Sold: US $57.5 million (2016)
a rare blue diamond, set into a ring, held up to the eye of a person- to show the scale of largeness.

Blue diamonds are prized for their size, depth of colour and colour saturation in the stone making this stone incredibly rare. The Oppenheimer Blue Diamond exemplifies all of these.

It’s crisp rectangular cut enhances colour concentration in the stone, a reminder that the cut choice of a diamond plays a critical role in how a diamond presents, whether at auction or being considered in a custom designed ring.

For clients considering coloured diamonds for bespoke jewellery, our Custom Design process allows full control over the stone selection, setting style, colours of metal, band profile and final proportions of the ring.

The Blue Moon of Josephine

When Colour Outranks Carat Weight

  • Carat weight: 12.03ct
  • Shape: Cushion cut
  • Colour: Fancy Vivid Blue (FVB)
  • Discovered: 2014
  • Sold: US $48.4 million (2015)
dark blue diamond set into a ring, blue moon of josephine blue diamond, held up to someones face for scale.

Despite its modest size relative to other famous diamonds, the Blue Moon of Josephine Diamond achieved one of the highest per-carat prices on record.

Its success shows an important lesson for buyers at every level: the quality and rarity of a diamond will always outweigh just the size alone, a principle we often discuss with our clients exploring high quality diamonds for engagement or milestone pieces of jewellery.

The Orange

One of the Rarest Diamond Colours Ever Discovered

  • Carat weight: 14.82ct
  • Shape: Pear
  • Colour: Fancy Vivid Orange (FVO)
  • Sold: US $35.5 million (2013)
the orange, a rare sizable natural diamond

Fancy Vivid Orange diamonds are among some of the rarest gemstones on earth. Their intense colour cannot be replicated or enhanced, it is purely natural.

While such stones are rarely on the market, understanding the fancy colour grading scale can be invaluable when considering unique centre stones. Our Diamond Education section explores how coloured diamonds are graded and valued.

The Cullinan Diamond

The Largest Diamond Ever Found

  • Original weight: 3,106ct (rough)
  • Discovered: 1905, South Africa
  • Purchased: £150,000 in 1907
2 carat diamond

The Cullinan Diamond stands apart from the commercial diamond market entirely.

Cut into more than 100 individual stones, including its largest cut diamond, Great Star of Africa weighting over 530cts on its own, it represents a moment in history where cutting craftsmanship, national pride, and natural wonder shine.

While few diamonds will ever rival it’s scale, the Cullinan Diamond reminds us that expert cutting is what unlocks a diamond’s true potential, a belief that sits at the heart of MDT DESIGN’s bespoke approach to jewellery.

The Hope Diamond

History, Myth, and Fascination

  • Carat weight: 45.52ct
  • Shape: Cushion antique brilliant cut
  • Colour: Fancy dark greyish-blue (FDGB)
The Hope Diamond, also known as "Le Bijou du Roi" one of the worlds most rare and expensive diamonds

With this stone now finding a home at the Smithsonian Institution, the Hope Diamond is valued as much for its legend as its gemmology.

Its antique cushion cutting style and incredibly deep colour highlight how diamond styles evolve over time.  A concept we often draw on when designing modern heirlooms inspired by classic forms through our Custom Design service.

Lesedi La Rona

A Modern Giant with a Transparent Price

  • Rough weight: 1,111ct
  • Discovered: 2015 in Botswana
  • Sold (rough): US $53 million (2017)
one of the worlds largest diamonds Lesedi La Rona help sizably in a hand

The Lesedi La Rona diamond is a rare example of a legendary diamond with a fully modern, documented journey given it was discovered in more recent times.

Its story reflects how today’s diamond world blends advanced technology with traditional craftsmanship, the same balance we apply when creating contemporary engagement rings designed to last a lifetime.

What the World’s Most Expensive Diamonds Teach Us

The most expensive diamonds in the world show us that true value is never accidental.

It comes from a combination of the following:

  • natural rarity that cannot be recreated
  • cutting craftsmanship that enhances the stone
  • stories that connect a stone to something more than generic

At MDT DESIGN, this philosophy informs everything we create, from timeless engagement rings to bespoke jewellery designed to become tomorrow’s heirlooms.

If you’re curious to explore further, we invite you to browse some of our incredible jewellery pieces, contact us to speak with an MDT DESIGN designer.