What is the most costly diamond in the world? If we use publicly documented auction results as the benchmark, the CTF Pink Star is the record holder for the highest price paid for a diamond or jewel at auction.

The 59.60-carat Fancy Vivid pink diamond sold for approximately US$71.2 million at Sotheby's Hong Kong in 2017. That public result is one of the clearest answers to searches for the most expensive diamond in the world, the costliest diamond in the world, and the world's most expensive diamond.

At the same time, words such as most valuable diamond in the world can mean something different from the highest auction price. Historical importance, exceptional rarity, natural color and provenance can give a diamond enormous significance even when it has not been sold publicly.

What Is the Most Expensive Diamond in the World?

The phrase most expensive diamond in the world is generally used to describe the diamond with the highest publicly reported selling price. By that measure, the CTF Pink Star is the key benchmark.

Sotheby's records show that the stone sold on April 4, 2017, for HK$553 million, approximately US$71.2 million. The diamond weighed 59.60 carats and was graded Fancy Vivid pink and Internally Flawless.

Because private transactions are not always disclosed, it is more accurate to describe this as the highest documented auction price rather than claiming that every diamond in private ownership has a known lower value.

Source: Sotheby's — CTF Pink Star

World Costly Diamond: What Does the Search Term Mean?

world costly diamond is a search phrase people use when looking for information about the world's highest-priced or most valuable diamonds. The wording is different from standard editorial English, but the underlying intent is usually the same: finding exceptional diamonds, record auction prices and famous gemstones.

Similarly, the costliest diamond in the world and costliest diamond in the world refer to the same broader subject. In this guide, auction records are used wherever a documented public price is available.

What Makes a Diamond So Expensive?

Diamond value is influenced by several characteristics rather than one simple measurement. For conventional colorless diamonds, the familiar 4Cs — carat weight, color, clarity and cut provide the foundation for understanding quality.

Exceptional diamonds may also command additional attention because of rare natural color, unusual size, historical provenance, certification, scarcity and collector demand.

This is why two diamonds with the same carat weight can have very different prices. A smaller stone with an exceptionally rare natural color can be more unusual than a much larger diamond with ordinary characteristics.

7 Most Expensive Diamonds: Major Public Auction Records

The phrase 7 most expensive diamonds is commonly used for lists of the highest-profile diamond auction results. The following examples are based on publicly documented sales and are presented as notable auction results rather than a claim that private diamond values are fully known.

Key public auction figures are documented by Sotheby's and Christie's. The CTF Pink Star sold for approximately US$71.2 million in 2017; the Williamson Pink Star for approximately US$57.7 million in 2022; the Oppenheimer Blue for approximately US$57.5 million in 2016; the Winston Pink Legacy for US$50.375 million in 2018; the Blue Moon of Josephine for approximately US$48.5 million in 2015; the Graff Pink for US$46.2 million in 2010; and the Princie Diamond for approximately US$39.3 million in 2013.

Sources: Sotheby's — CTF Pink Star · Sotheby's — Williamson Pink Star · Christie's — Winston Pink Legacy · Christie's — Oppenheimer Blue

The Most Expensive Diamond Ever Sold: CTF Pink Star

The most expensive diamond ever sold at a documented public auction is the CTF Pink Star. Its combination of very large size, Fancy Vivid pink color and Internally Flawless clarity made it an exceptional gemstone.

The stone was cut from a 132.5-carat rough diamond and ultimately became a 59.60-carat polished gemstone. Sotheby's described it as the largest Flawless or Internally Flawless Fancy Vivid pink natural-color diamond graded by GIA at the time.

Source: Sotheby's — The Pink Star

The Rarest Diamonds in the World

Searches for rarest diamonds, rare diamonds, and rarest diamond can refer to many different forms of rarity. A diamond may be unusual because of color, size, clarity, geological characteristics, provenance, or a combination of these.

GIA explains that saturated pinks, blues and greens are among the rarest and most valuable fancy-color categories. Red diamonds are also exceptionally rare.

For this reason, the answer to what is the rarest diamond is not necessarily one specific gemstone. Different criteria can produce different answers.

What Is the Rarest Diamond in the World?

When someone asks what is the rarest diamond in the world, the correct answer depends on what kind of rarity is being measured.

If natural fancy color is the focus, exceptionally strong pink, blue, green and red diamonds can be extremely uncommon. GIA notes that color intensity and hue can have a major impact on the rarity and value of fancy-color diamonds.

Therefore, the rarest diamonds in the world are not necessarily the biggest stones. Rarity often comes from an unusual combination of multiple characteristics.

The search phrase the most rare diamond in the world generally points to this same question about exceptionally scarce natural diamonds.

Source: GIA — Fancy Color Diamond Buyer's Guide

Most Rare Diamond: Why Rarity Is Difficult to Define

A search for the most rare diamond can mean a diamond with the rarest color, the largest size within a rare color category, exceptional clarity, or a particularly unusual combination of traits.

In practice, rarity should be described carefully. One diamond may be exceptionally rare because of its natural red color, while another may be famous for combining large carat weight with vivid blue or pink color.

How Much Are Diamonds Worth?

The question how much are diamonds worth does not have one universal answer. Diamond prices vary according to the individual stone's characteristics, market conditions, origin and certification.

Likewise, how much is a diamond worth depends on its carat weight, color, clarity, cut and other factors. A rare fancy-color diamond may have a completely different value profile from a conventional colorless jewellery diamond.

The search phrase how much diamond is worth usually asks the same underlying question: what characteristics determine a diamond's market value?

Highest Price Diamond: What Does the Auction Record Show?

Searches for the highest price diamond often refer to the highest public auction result. The CTF Pink Star's approximately US$71.2 million sale is the clearest documented benchmark.

However, an auction record should not be confused with the highest possible private valuation. Private sales can involve confidentiality, different market circumstances and stones that are never publicly offered.

Biggest Diamond in the World Price

The phrase biggest diamond in the world price can be confusing because the biggest known rough diamond and the most expensive diamond sold at auction are not the same thing.

The Cullinan is famous as the largest gem-quality diamond crystal discovered, with a rough weight of approximately 3,106 carats. It was subsequently cut into several major stones, including Cullinan I and Cullinan II.

Because the original rough Cullinan is no longer an intact gemstone available for ordinary market sale, there is no simple current retail largest diamond in the world price.

Source: Sotheby's — Cullinan background

Largest Diamond in the World Value

The largest diamond in the world value is not a standard market figure. The value of the original Cullinan is often estimated differently depending on whether someone is discussing the rough stone, its polished descendants, historical significance or hypothetical market value.

The same applies to the phrase biggest diamond in the world value. A historical or royal gemstone may be impossible to price accurately because it is not being offered for sale.

Cullinan Diamond Price, Worth & Value

The Cullinan diamond price is difficult to state as a current market figure because the original rough Cullinan was cut more than a century ago and is no longer traded as one intact stone.

Searches for diamond cullinan price, price of cullinan diamond and cullinan diamond price usually refer to the famous original rough stone or one of its major polished descendants.

The Cullinan weighed approximately 3,106 carats in rough form. It was cut into nine major stones and numerous smaller stones. Cullinan I weighs 530.2 carats, while Cullinan II weighs 317.4 carats.

Because the original diamond no longer exists as one marketable rough gemstone, the cullinan diamond worth and cullinan diamond value are normally discussed as historical or hypothetical estimates rather than a verified current sale price.

In particular, the question how much is the Cullinan diamond worth cannot be answered with a current public auction price for the original rough stone because that intact stone is no longer on the market.

Hope Diamond Price, Cost & Historical Value

The Hope Diamond is another famous example where price and historical value should not be confused.

The Smithsonian lists the Hope Diamond at 45.52 carats and describes it as a natural fancy dark grayish-blue diamond. It is part of the Smithsonian collection and is not presented as an ordinary market gemstone for sale.

This is why searches for hope diamond price, hope diamond cost and price of the hope diamond need context. A precise current retail price does not exist in the same way it does for an actively sold jewellery diamond.

The same applies to hope diamond how much is it worth and what is the hope diamond worth: any estimated figure should be identified as an estimate rather than a current public selling price.

Another frequent question is whether the hope diamond the most expensive diamond is accurate. The Hope Diamond is one of the world's most famous historic diamonds, but it is not the documented auction-price leader; the CTF Pink Star holds that public auction benchmark.

Source: Smithsonian — Hope Diamond

Why Fancy-Color Diamonds Can Be So Valuable

Color plays an unusual role in fancy-color diamonds. GIA explains that saturated pinks, blues and greens are among the rarest and most valuable fancy-color diamonds.

Even small differences in hue, tone and saturation can affect market value. For this reason, two diamonds with similar carat weights can have very different values if their natural colors are substantially different.

Blue diamonds are especially notable because their color can be associated with boron, while natural red and strongly saturated pink diamonds are exceptionally scarce.

Source: GIA — Fancy Color Diamond Quality Factors

Natural Diamonds vs Lab-Grown Diamonds

Natural diamonds form through geological processes, while laboratory-grown diamonds are produced through controlled technological processes such as CVD and HPHT.

GIA states that laboratory-grown diamonds have essentially the same chemical composition and crystal structure as natural diamonds. Their growth origin can be identified through specialized gemological examination.

Natural and lab-grown diamonds can have substantially different market prices, so buyers should compare diamonds within the same category and review the actual specifications rather than relying on carat weight alone.

Explore STAR Jewellery's lab-grown diamond jewellery collection for modern diamond designs.

How Diamond Certification Helps Buyers

When purchasing a diamond, grading documentation can help buyers understand characteristics such as carat weight, color, clarity and other identifying details.

For laboratory-grown diamonds, documentation can also help identify the diamond's laboratory-grown origin and relevant grading characteristics.

When comparing a diamond value or jewellery price, review the complete specification rather than judging the stone from its carat weight alone.

Source: GIA — Natural and Laboratory-Grown Diamonds

Shop Diamond Jewellery at STAR Jewellery

The record-setting diamonds discussed above are exceptional collector gemstones. For jewellery shoppers, STAR Jewellery offers natural and lab-grown diamond designs in a range of styles, shapes and settings.

Explore these real STAR Jewellery diamond pieces below, then browse the relevant collections for more designs.

14K Gold Three Flower Diamond Ring

A detailed gold diamond ring design for shoppers looking for a distinctive jewellery style.

View Product

Solid Gold Mountain Diamond Ring

A contemporary solid-gold diamond ring with a distinctive architectural-inspired silhouette.

View Product

Diamond Open Wrap Around Ring

A modern open-wrap silhouette with diamond detailing and solid-gold construction.

View Product

14K Solid Gold Stackable Natural Diamond Wedding Ring

A slim natural diamond wedding band designed for stacking and everyday wear.

View Product

Explore more styles in our diamond rings, engagement rings and lab-grown diamond rings collections.

Explore Heart-Shaped Diamond Jewellery

Heart-shaped diamonds are a popular choice for romantic jewellery. STAR Jewellery has a dedicated heart cut diamond jewellery collection featuring heart-shaped diamond designs.

If you are shopping specifically for engagement jewellery, explore our engagement rings collection for additional shapes and settings.

Frequently Asked Questions

Keep Shopping

Sources & Further Reading

Sotheby's — CTF Pink Star
Sotheby's — Williamson Pink Star
Christie's — Winston Pink Legacy
Christie's — Oppenheimer Blue
Sotheby's — Blue Moon of Josephine
GIA — Fancy Color Diamond Buyer's Guide
Smithsonian — Hope Diamond