Ruby: The King of Gemstones

Ruby is one of the most coveted gemstones in the world. Known as the "king of gems" in ancient Sanskrit texts, the ruby belongs to the corundum mineral family alongside sapphire. What separates a ruby from a sapphire is the presence of chromium, which gives the stone its signature red colour. From the legendary pigeon blood rubies of Myanmar to the vibrant stones of Mozambique, rubies have been treasured for millennia and continue to command some of the highest per-carat prices of any gemstone.

Ruby Properties and Characteristics

Ruby is the red variety of the mineral corundum (aluminium oxide, Al₂O₃). It rates 9 on the Mohs hardness scale, making it the second hardest natural gemstone after diamond. This exceptional hardness makes ruby an outstanding choice for all types of jewellery, including engagement rings and everyday pieces.

The colour of a ruby ranges from pinkish-red to deep purplish-red, with the most prized shade being a vivid, saturated red with a slight blue undertone, traditionally described as "pigeon blood." Rubies can also display a phenomenon called asterism, where a six-rayed star appears on the surface of cabochon-cut stones. These are known as star rubies, and the finest examples are highly collectible.

Ruby Colour Grading

Colour is the single most important factor in determining a ruby's value. Gemmologists evaluate ruby colour using three components:

• Hue – The dominant spectral colour. The finest rubies are pure red, sometimes with a slight purplish or pinkish secondary hue.
• Saturation – The intensity of the colour. Top rubies show vivid saturation without appearing too dark or too light.
• Tone – The lightness or darkness of the colour. Medium to medium-dark tones are most desirable. Stones that are too dark appear almost black, while overly light stones may be classified as pink sapphire rather than ruby.

The boundary between ruby and pink sapphire is one of the most debated topics in gemmology. Different laboratories apply slightly different criteria, which is why the choice of lab report matters when purchasing high-value stones.

Pigeon Blood Ruby

The term "pigeon blood" historically referred to the finest rubies from the Mogok Valley in Myanmar. Today, it is used by gemmological laboratories such as Gubelin and SSEF to describe rubies that meet specific colour criteria: a vivid red with medium to medium-dark tone and strong fluorescence. Pigeon blood rubies command a significant premium, sometimes two to three times the price of comparable rubies without the designation.

Sources and Origins

Ruby deposits are found across multiple continents, and origin has a measurable impact on value.

Myanmar (Burma)

The Mogok Valley in Myanmar has produced the world's most famous rubies for over 800 years. Burmese rubies are renowned for their intense colour, strong fluorescence, and characteristic "silk" inclusions that can create a soft, glowing appearance. In the early 2000s, the Mong Hsu deposit became an important secondary source, though these stones typically require heat treatment.

Mozambique

Since around 2009, the Montepuez ruby deposit in Mozambique has emerged as one of the most significant ruby sources in the world. Mozambican rubies can rival Burmese stones in colour and quality, and top specimens have sold for millions at auction. Their slightly higher iron content gives them a marginally different fluorescence profile compared to Burmese stones.

Other Sources

Notable ruby deposits also exist in Thailand, Sri Lanka, Madagascar, Tanzania, Vietnam, and Afghanistan. Thai rubies tend to be darker with brownish secondary hues, while Sri Lankan rubies often display lighter, pinkish tones.

Ruby Treatments

The majority of rubies on the market have been treated in some way to improve their appearance. Understanding treatments is essential for making an informed purchase.

• Heat treatment – The most common and widely accepted enhancement. Heating rubies to temperatures between 1,200 and 1,800 degrees Celsius can improve colour and clarity. Heat-treated rubies are generally valued lower than untreated stones of similar quality but remain highly desirable.
• Flux healing – During heat treatment, a flux such as borax may be used. This can heal fractures within the stone by dissolving and re-depositing corundum. Moderate flux residue is widely accepted, but significant amounts reduce value.
• Lead glass filling – Fractures are filled with lead glass to improve transparency. This treatment dramatically lowers a ruby's value and durability. Lead-glass-filled rubies require special care and should always be clearly disclosed.
• Beryllium diffusion – Beryllium is diffused into the stone at high temperatures to alter colour. This treatment is more common in sapphires but occasionally seen in rubies.

Ruby Pricing

Ruby prices vary enormously based on colour, clarity, size, treatment status, and origin. As a general guide:

• Commercial-grade rubies (heated, included): $100 – $1,500 per carat
• Fine-quality rubies (heated, good colour): $2,000 – $15,000 per carat
• Top-quality rubies (unheated, vivid colour, clean): $20,000 – $100,000+ per carat
• Exceptional Burmese pigeon blood rubies over 5 carats: $200,000 – $1,000,000+ per carat at auction

The record price for a ruby at auction was set in 2015 when the 25.59-carat Sunrise Ruby sold for over $30 million, equating to roughly $1.2 million per carat.

How to Buy a Ruby

When purchasing a ruby, keep these guidelines in mind:

• Prioritise colour – Colour matters more than clarity in rubies. A stone with minor inclusions but outstanding colour will always be more valuable than a clean stone with poor colour.
• Request a laboratory report – For any ruby over one carat, obtain a report from a respected lab such as GIA, Gubelin, SSEF, or AGL. The report will confirm natural origin, disclose treatments, and may include an origin determination.
• Understand the treatment – Ask specifically whether the stone has been heated, and if so, whether flux residues are present. Avoid lead-glass-filled rubies for fine jewellery.
• Compare in different lighting – Rubies can appear different under incandescent, fluorescent, and natural light. Fine rubies look their best under a range of lighting conditions.
• Consider the setting – Rubies pair beautifully with both yellow gold and white gold or platinum. Yellow gold enhances warmth, while white metals create a striking contrast. See our jewellery styles guide for inspiration.

Ruby in Jewellery

With a hardness of 9, rubies are suitable for all types of jewellery. They are a classic choice for engagement rings, cocktail rings, pendants, earrings, and tennis bracelets. Ruby engagement rings have gained significant popularity as an alternative to traditional diamond rings, offering bold colour and exceptional durability.

Star rubies are typically cut as cabochons to display their asterism and make dramatic statement pieces. Smaller rubies are frequently used as accent stones in jewellery designs featuring diamonds as the centre stone.

Ruby Care and Cleaning

Rubies are extremely durable and generally easy to care for. Untreated and heat-treated rubies can be cleaned with warm soapy water and a soft brush, and are generally safe for ultrasonic and steam cleaners. However, if your ruby has been fracture-filled or glass-filled, avoid ultrasonic cleaners, steamers, and harsh chemicals, as these can damage the filling. For comprehensive advice, see our jewellery care guide.

Conclusion

Ruby remains one of the most prestigious and desirable gemstones in the world. Its combination of exceptional hardness, vivid colour, historical significance, and enduring beauty makes it a timeless choice for fine jewellery. Whether you are investing in a museum-quality pigeon blood ruby or selecting a beautiful heated stone for an engagement ring, understanding the factors that drive quality and value will ensure you make a purchase you treasure for a lifetime.