Sapphire, Ruby, or Emerald? A Guide to Coloured Gemstone Engagement Rings
The diamond engagement ring is a twentieth-century convention, not an ancient tradition. For most of jewellery history, coloured gemstones — sapphires, rubies, emeralds, and many others — were as likely to appear at the centre of an important ring as a diamond was. The choice of a coloured centre stone is not unconventional. It is, in many ways, a return to a longer tradition.
At Diamond Ateliers, we design coloured gemstone engagement rings frequently — either with a coloured stone as the sole centre stone, or in combination with diamonds in three-stone and toi et moi configurations. This guide covers the three most popular coloured stone choices and what makes each one distinct.
Sapphire
The blue sapphire is the most popular coloured stone for engagement rings, a status it has held since Prince Charles gave Princess Diana a 12-carat oval Ceylon sapphire ring in 1981 — now worn by the Princess of Wales. The association with royalty runs deeper than that single ring: sapphires have been used in royal engagement jewellery across centuries and cultures.
Hardness and Durability
Sapphire scores 9 on the Mohs hardness scale — second only to diamond among commonly used gemstones. It is an excellent choice for daily wear in a ring. The risk of scratching in normal use is negligible.
Colour Range
"Sapphire" refers to any gem-quality corundum that is not red (red corundum is ruby). The most prized colour is the vivid cornflower blue of Ceylon (Sri Lankan) sapphires, but sapphires occur in almost every colour: royal blue, teal, violet, pink, yellow, peach, and the highly prized padparadscha — a rare salmon-pink-orange variety from Sri Lanka that commands extraordinary prices for fine specimens.
The most sought-after origins are Sri Lanka (Ceylon) and Kashmir, with Burma (Myanmar) sapphires also commanding premiums. For most clients, a well-coloured Ceylon sapphire represents the best combination of quality, availability, and value.
What to Look for
Unlike diamonds, sapphires are not graded on a standardised international scale. Colour is assessed visually: saturation, tone, and hue all contribute to the quality judgment. For blue sapphires, the ideal is a medium to medium-dark vivid blue with no visible grey or green modifier. Clarity is assessed differently than for diamonds — sapphires are a Type II gemstone, meaning inclusions are expected and do not disqualify an otherwise beautiful stone the way they might a diamond. Eye-clean is a good standard; some inclusions add character without affecting beauty.
A certificate from GGL, GIA, or Gübelin — particularly for higher-value stones — confirming natural origin and, ideally, geographic origin, is important when buying a sapphire.
Ruby
Ruby is red corundum — the same mineral species as sapphire, coloured red by chromium. Fine rubies are among the rarest and most valuable gemstones in the world: a top-quality Burmese ruby of significant size can exceed a diamond of equal weight in price by a considerable margin.
Hardness and Durability
Like sapphire, ruby scores 9 on the Mohs scale and is an excellent choice for daily wear.
Colour
The most prized ruby colour is "pigeon's blood" — a vivid, pure red with a slight blue fluorescence that gives the stone an almost luminous quality under light. This colour is associated with Burma (Mogok Valley), the most prestigious ruby origin. Thai, Mozambican, and Sri Lankan rubies are also excellent and more commercially available.
For most engagement ring buyers, a vivid, medium-dark red ruby with no visible brown or orange modifier is the target. Very dark rubies lose their luminosity; very light rubies shade into pink sapphire territory — a distinction that matters for value but less so for beauty in some cases.
What to Look for
Heat treatment is standard practice for rubies and accepted in the trade — it improves colour and clarity and does not diminish value the way some other treatments do. What to avoid is glass-filling treatment, which significantly lowers a stone's durability and value. A certificate confirming natural origin and treatment status is essential for any ruby purchase above modest value.
Emerald
The emerald is the most fragile of the three stones discussed here, and the most distinctive. Its saturated green — from trace chromium and vanadium — is unlike any other natural colour in the gem world. Cleopatra's legendary love of emeralds is one of the earliest recorded instances of a gemstone acquiring personal meaning for its wearer.
Hardness and Durability
Emerald scores 7.5–8 on the Mohs scale — significantly softer than sapphire or ruby, and more susceptible to scratching. More importantly, almost all emeralds contain natural fractures and inclusions (called a "jardin" — garden) that can make the stone vulnerable to chipping or cracking under impact. For an engagement ring worn daily, this requires a protective setting: a bezel or a setting with good coverage of the stone's girdle and corners is important. An open four-prong solitaire is higher risk for an emerald than for a diamond or sapphire.
Colour
The most prized emerald colour is a vivid, saturated green with a slightly bluish secondary hue, associated with Colombian origin — particularly the Muzo and Chivor mines. Zambian emeralds are the other major fine-quality source and tend toward a slightly more blue-green tone. Colombian and Zambian emeralds are both beautiful; origin preference is partly cultural and partly personal.
What to Look for
Almost all emeralds are treated with oils or resins to fill surface-reaching fractures — this is accepted practice in the trade, though the degree of treatment matters significantly for value. "Minor" or "insignificant" treatment is standard and acceptable; "significant" or "heavily" treated stones are worth considerably less. A certificate from GIA, GRS, or Gübelin specifying treatment level is essential for any emerald purchase of value.
For daily-wear engagement rings, selecting an emerald with good overall structure — no fractures that run deeply across the stone — and pairing it with a protective setting is the most important practical decision.
Choosing Between the Three
If durability for daily wear is the primary concern: sapphire or ruby, both at hardness 9, are the most practical choices. Emerald requires more care and a more protective setting.
If colour is the primary concern: this is entirely personal. Blue sapphire is the most versatile and widely flattering. Ruby is the most dramatic and the most historically significant. Emerald is the most distinctive and the most immediately recognisable.
If the choice is for a specific person with a specific aesthetic: bring that person in. The only reliable way to know whether a blue sapphire, a ruby, or an emerald is the right stone for a specific hand and a specific personality is to see them together in person.
Talk to Us
At Diamond Ateliers, we source coloured gemstones as carefully as we source diamonds — with certificates, direct evaluation, and an honest assessment of what a given stone's quality and origin are worth. If you are considering a coloured gemstone centre stone, come in for a conversation.
Visit us at 176 Orchard Rd, #03-05 The Centrepoint, Singapore 238843. Consultations are by appointment and without obligation.