15 must-know facts about rubies unveiled by L’Ecole Asia Pacific, School of Jewelry Arts

Education is empowerment, and that’s the mission of L’Ecole, School of Jewelry Arts. Supported by luxury French jeweller Van Cleef & Arpels, it was established in 2012 on Place Vendome in Paris as an initiation school, open to everyone curious about jewellery culture.

Offering courses in the three major fields of jewellery history, gemstones, jewellery-making savoir faire, classes are all practice-based and taught by art historians, gemologists, jewellers and artisans. 

The success of this community-building institution has seen it expand around the world, from other permanent locations to another one in Paris, as well as Hong Kong, Dubai, and Shanghai. Regularly travelling abroad to host talks, exhibitions, or programmes that can last one to three weeks, its Asia-Pacific branch recently made a pit stop in Singapore for a ruby exposition.

For a jewellery editor, this experience was a dream come true. While I’ve been privileged to view and touch many ruby jewels over the years, they were the finished products. What about the stories of the mines, the gem’s historical importance, and the adventures of the geologists? 

Short of signing up for a GIA course, which focuses on technical training, there was simply no way one could gain comprehensive first-hand exposure, until L’Ecole made it happen. 

Through a public exhibition at Van Cleef & Arpels’ Les Jardins Secrets space in Raffles Hotel’s Arcade, and then a by-invitation hands-on workshop helmed by experts and a talk presenting Billie Hughes, photomicrographer and gemologist of Bangkok-based Lotus Gemology, I gained a deeper understanding of the secret universe of the ruby in a little over three hours. 

Here are the top 15 interesting insights that could enhance your knowledge as a gem and jewellery lover.

1. The corundum conundrum

Rubies and sapphires are both varieties of the mineral family known as corundum, which is primarily composed of aluminium oxide with miniscule amounts of chemical elements that include iron, titanium, chromium, vanadium, nickel, cobalt, boron, and silicon.

The main difference between the two gems lies in the main elements colouring them. Predominant amounts of trace chromium, typically less than 0.2 per cent, produce a vibrant red hue, the defining trait of rubies in gemology.

The mineral is identified as a sapphire when it exhibits any other colour, with an extensive palette beyond rainbow shades. The key trace elements, as well as their combination and concentration, determine the final hue. Pink sapphires have lower levels of chromium than rubies. Classic blue sapphires are formed with iron and titanium in their crystal structure; orange and purple varieties with iron and chromium; and yellow and green gems with iron.

2. Far and away

Rubies are mined in regions worldwide, each known for producing distinct features. Rubies from Thailand are often associated with volcanic activity, which imparts a particular dark hue. Those from the Himalayas are renowned for their intense red colour with high fluorescence, often due to the marble mother rock they are found in. This is the same for Burmese rubies, whose origins are closely associated with the Himalayan mountain formation.

Mozambique has emerged as a significant source, where rubies are found in amphibole-related rocks, producing stones of one-of-a-kind qualities. Greenland is also notable for its ancient rubies, some of the oldest on earth, dating back 2.7 billion years, and found in feldspar- and mica-rich basaltic rocks. Other regions, like China, produce opaque dark rubies whose quality is often poor.

3. Historical symbolism

The stone holds immense significance across civilisations and historical eras, mainly due to its intense red colour, which connotes power, vitality, and divine authority. In ancient cultures like Egypt and Japan, red was associated with the sun, life, and protection, often represented in art and mythology. 

Throughout the Middle Ages, rubies were revered for their representation of fire and light, connected with concepts of immortality and divine protection, as seen in the crowns of European monarchs and religious relics. Ancient texts like those of Pliny the Elder and Theophrastus classified rubies based on their bright red hue, often referring to them as “carbunculus” in Latin, meaning small burning coals. 

In South Asia, rubies were associated with powerful rulers like the Mughals, who wore these gems as symbols of authority and victory in battle. 

4. Different eyes

The perception of what makes a ruby can vary widely from person to person, influenced by eyesight, lighting conditions, and even cultural backgrounds. Colour is not an absolute experience; reasons such as a person’s sensitivity to specific wavelengths, the angle of viewing, and environmental lighting can all impact how the ruby’s red hue is perceived. 

For example, one person may see a deep red, while another might notice purplish or pinkish undertones in the same stone. One may perceive a corundum as a ruby, while another may perceive it as a pink sapphire. Cultural factors also come into play, as different regions may have varying standards for the ideal “ruby red”. 

5. Let there be light

The subjectivity of an individual’s perception is further complicated by the fact that natural or artificial lighting alters the stone's appearance. Gemologists use standardised lighting, with the most common set at a neutral, balanced colour temperature of around 5,500 Kelvin, which closely resembles natural daylight. 

Additionally, the hue of a ruby can also shift depending on the viewing angle — a phenomenon known as pleochroism. In rubies, it typically results in a primary red hue that may display secondary shades, such as orangey-red or purplish-red, when viewed from different perspectives. These variations are often influenced by the cut and crystal orientation, making the ruby appear to shift in tone and saturation. 

6. Best-kept secrets

In gemological laboratories, graders rely on a master set of coloured gemstones to evaluate and compare the colours of gems submitted for grading. A closely guarded secret, it consists of reference stones with established hues, tones, and saturation levels, serving as a crucial benchmark for assessing the colour quality of gemstones.

Each lab develops its own proprietary set and criteria, unfortunately creating inconsistencies in grading, especially when it comes to high-value stones like rubies or sapphires. 

7. The fact about fluorescence

Fluorescence in rubies is crucial in enhancing their red appearance by balancing out any bluish or purplish tints that may be present due to light absorption in the blue spectrum. This fluorescence occurs when rubies are rich in chromium but low in iron, as too much of the latter can suppress the effect. This phenomenon and other factors can influence the perception of the ruby’s colour.

8. Trick of the trade

Certain undertones, like purplish or bluish hints, may become more pronounced or subdued in indoor settings with artificial lighting, such as white or yellow light. Fluorescent lighting can also exaggerate or diminish the ruby’s fluorescence, making the stone appear more vibrant or duller. L’Ecole’s experts advise buyers to examine rubies under different lighting conditions to get a true sense of the stone's colour, as some lights, particularly those designed for retail displays, are engineered to enhance the gem's appearance. 

9. Farewell, pigeon’s blood

The term “pigeon’s blood” used to describe the finest rubies originated as a marketing term rather than a scientific classification, and its exact origins are mired in myths and stories. Some believe the name refers to the deep red colour of a pigeon’s eye, while others claim it comes from the first drops of a pigeon’s blood when the bird is killed. 

While the romanticism surrounding “pigeon’s blood” rubies has contributed to their premium pricing, no one classification remains. Experts, therefore, advise buyers to focus on the beauty and appeal of the ruby itself rather than rely solely on the “pigeon’s blood” designation in reports.

10. Size matters

Rubies are typically small because larger, untreated rubies are remarkably rare. Finding a ruby of one carat without treatment is already considered difficult, and discovering rubies over three or five carats is highly uncommon.

We were shown a ruby weighing 25.76 carats during the workshop, highlighted as exceptionally large. However, the formation process of rubies, including natural heating and the conditions within the earth, often results in smaller stones. Furthermore, the cutting of rubies prioritises the preservation of the stone’s colour and weight rather than achieving perfect proportions, further contributing to the prevalence of small sizes in the market.

11. Not all reds are the same

Throughout history, red spinel has often been mistaken for ruby due to its strikingly similar red hue, which made it difficult to distinguish between the two before modern gemological techniques emerged. This confusion was especially prevalent during the Middle Ages and earlier, when gemstones were primarily classified by colour rather than chemical and atomic properties. 

Both rubies and red spinels were adored in antiquity, leading to their interchangeability in crowns, religious artefacts, and royal jewels. Famous examples of this mix-up include the Black Prince’s Ruby in the British Imperial Crown, which is actually a large red spinel, and the Bohemian Crown Jewels, in which a ruby turned out to be a rubellite.

The Mughal emperors, known for their vast gemstone collections, prized large red spinels, calling them “lal”, which translates to gem. This further blurred the distinction between spinels and rubies. It wasn't until the 19th century that gemology science began categorising these gems correctly.

12. Natural vs treated

The micro-structure and inclusions in non-heat-treated rubies differ significantly from those that have undergone heat treatment. In non-heat-treated rubies, natural inclusions such as rutile needles (silk), crystal clusters, and mineral clouds are often intact, contributing to the stone's organic beauty and providing vital clues about its origin.

These inclusions can create optical effects, enhancing the gem’s desirability without diminishing its value. Conversely, heat-treated rubies are subjected to high temperatures to improve clarity and colour, often dissolving or reducing the visibility of inclusions like rutile needles.

The treatment may enhance the ruby's transparency and saturation. Still, it also alters the natural internal structure, sometimes creating glassy fractures or melting inclusions, making the gem look cleaner but less unique. 

13. Smooth as velvet

The optical effect known as silk was put on show in Billie Hughes’ photos displayed at the exhibition. It is caused by tiny, needle-like rutile inclusions naturally embedded within the gemstone. Arranged in intersecting patterns, scattering light as it passes through the stone, these result in a diffused glow and velvety sheen rather than sharp brilliance. 

Silk is particularly prized in Burmese rubies, where it adds a distinctive softness and luxurious texture to the gem. Rather than diminishing the stone’s value, this optical phenomenon enhances its beauty, especially in untreated stones, where rutile needles indicate natural origins and contribute to the ruby’s character and allure.

14. Mystery revealed

Van Cleef & Arpels’ Mystery Set technique is one of the most remarkable innovations in high jewellery craftsmanship. It allows coloured gemstones to be set with no visible prongs or metal. Developed in the 1930s, this labour-intensive method involves meticulously carving grooves into the sides of each gem, which are then slid into a hidden gold framework. 

The result is a seamless, fluid appearance where the gemstones seem to float, highlighting rubies’ rich, velvety character. At an activity station at the exhibition, a large prop allowed visitors a hands-on experience of sliding individual “rubies” into a metal structure. It was nearly impossible without adequate skill and a practised hand, which reminded us of the incredible skills the maison’s artisans must possess to accomplish it on a micro-scale.

15. Abracadabra

In addition to the Mystery Set, Van Cleef & Arpels is renowned for its expertise in transformable jewellery, creating pieces that can be worn in multiple ways. This versatility appeals to its ruby creations, such as necklaces that can be reconfigured into bracelets or brooches, offering beauty and function in exquisite, timeless designs.