Sapphire and ruby are both corundum, a very hard gemstone that wears well every day, while spinel is a separate mineral that is a little softer but still well suited to an engagement ring. Sapphire offers the widest range of colours, ruby is the classic red, and spinel gives bright colour and sparkle that many people find surprising.
All three are popular for coloured engagement rings. Here is how they compare.
The basics
| Sapphire | Ruby | Spinel | |
|---|---|---|---|
| Mineral | Corundum | Corundum | Spinel |
| Hardness (Mohs) | 9 | 9 | About 8 |
| Colours | Blue and almost every other colour except red | Red | Red, pink, blue, purple, grey and more |
| Commonly heat treated? | Often | Often | Less often |
Diamond sits at 10 on the Mohs scale, and sapphire and ruby, at 9, are among the hardest gemstones after diamond and moissanite. Spinel sits at about 8.
Sapphire and ruby: the same stone in different colours
Ruby is simply red corundum. When corundum is any other colour, it is called sapphire. Blue is the classic, but sapphires also come in pink, yellow, green, teal, purple and white. Our guide to salt and pepper, teal and parti sapphires covers some of the less usual types.
Where pink ends and red begins is not fixed, so the same stone can be described differently by different sellers. A gemmological report helps.
Illustration of a CAD drawing of a red gemstone halo ring, not a finished À Vie piece.
Spinel: the stone often mistaken for ruby
Red spinel and ruby can look very alike, and for centuries they were confused. One of the best known examples is the Black Prince's Ruby in the Imperial State Crown, which is in fact a spinel, as the Royal Collection Trust notes. Today spinel is valued in its own right for its bright colour and lively sparkle.
Spinel is singly refractive, which can give it a clean, vivid colour. It is also commonly sold without heat treatment, which some buyers prefer. Our spinel gemstone guide goes into more depth.
Which is most durable?
Sapphire and ruby are harder than spinel and resist scratches very well. Spinel, at about 8, is still hard enough for daily wear, and it has no cleavage, which means it is less likely to split along a plane than some other gems. With a sensible setting, all three can give many years of everyday wear.
For a ring worn every day, protective settings such as a bezel or a halo can help any coloured stone, especially if you work with your hands.
Colour and how it looks in a ring
- Sapphire gives you the most choice, from deep blue to soft pastels.
- Ruby is about red, and the most sought after rubies have a strong, saturated colour.
- Spinel comes in many shades,, from reds and pinks to blues and purples.
Metal choice changes how each stone reads. Yellow gold warms reds and pinks, while white metals make blues look cooler and crisper.
Treatments and reports
Many sapphires and rubies are heated to improve colour or clarity. It is a widely accepted practice, but treatment affects value, so it should be disclosed. Some rubies receive more extensive treatments, such as glass filling, which makes them less durable and needs more careful handling. For any significant coloured stone, ask for a report from a recognised gemmological laboratory.
How to choose
If you want the toughest coloured option, sapphire or ruby is a strong choice. If you love red but want something a little different, or prefer untreated stones, spinel is well worth a look. The ruby guide, ruby rings: a complete guide, has more on choosing a ruby.
Exploring coloured stones with us
Whether you lean towards sapphire, ruby or spinel, we would check what can be sourced and talk through treatment and reports before you commit. A 70% deposit starts the making once you approve the CAD design. Your ring is crafted by specialist goldsmiths, UK hallmarked and sent by insured tracked courier. Bespoke rings start from £600.
Read about the bespoke journey to see how a commission works from first conversation to delivery.
Frequently asked questions
Is spinel as durable as sapphire?
Spinel is slightly softer, about 8 on the Mohs scale against 9 for sapphire, but it is still hard enough for daily wear.
Are ruby and sapphire the same stone?
Yes. Both are corundum. Ruby is the red variety, and every other colour is called sapphire.
Is spinel usually treated?
Spinel is commonly sold without heat treatment, while many sapphires and rubies are heated. Ask for a report to be sure.
Which is best for an engagement ring, spinel, sapphire or ruby?
All three can work. Sapphire and ruby are harder, while spinel offers bright colour and is often untreated.