Most people arrive at coloured stones by elimination. They have decided a white diamond is not the thing, they have looked hard at sapphire, and then they want to know what else exists before committing.
Three names come up more than the rest: spinel, tourmaline and zircon. These are the alternative gemstones engagement ring buyers keep asking about, and they tend to get described interchangeably, as though picking between them is a matter of taste. It is not. Each one behaves differently on a hand that gets used every day, and the gap between them is wide enough to change which you should buy.
We should declare the obvious conflict of interest first. We specialise in Australian sapphires, so we have every commercial reason to steer you back towards corundum. Take what follows with that in mind. There is at least one stone on this list that beats sapphire at something we care about.
The Alternative Gemstones Engagement Ring Buyers Ask About Share One Problem
None of them is corundum. Sapphire sits at 9 on the Mohs scale, and the three stones here sit below it. That matters, but not in the simple way most articles imply.
The GIA splits durability into three separate properties, and they are worth keeping apart in your head. Hardness is resistance to scratches and abrasion. Toughness is how well a stone resists breaking and chipping, which comes down to how its atoms bond together. Stability is how it copes with chemicals, light, and changes in temperature. A stone can score well on one and badly on another, and the failure you actually experience depends on which one you tested without meaning to.
The Mohs scale also misleads people because it is not linear. It ranks stones relative to each other, nothing more. The GIA makes the point bluntly: corundum is a 9 and diamond is a 10, but diamond is many times harder. The same compression operates lower down the scale. A 7.5 is not five per cent softer than an 8 in any way you could measure with a scratch test.
So read the numbers below as a rough ordering, then read what each stone actually does. We covered this ground for sapphire in our piece on sapphire hardness and everyday wear, and the same logic applies here.
Spinel Is the One That Can Beat Sapphire
Spinel is magnesium aluminium oxide, it crystallises in the cubic system, and it is singly refractive with no birefringence at all. That last point is the whole argument for it. Light passes through spinel the same way in every direction, so there is no pleochroism, no second colour appearing as you turn the stone, and no doubling of the back facets seen through the table. You get one colour, evenly, from every angle. Sapphire cannot make that claim, and anyone who has watched a client tilt a sapphire under studio lights and go quiet knows why it matters.
It ranks 8 on the Mohs scale with good toughness, and it is stable in light and chemicals. High heat can fade some spinel colours, which is a workshop consideration rather than a wearing one.
Then there is the honest part, and it is the reason this article exists. The GIA's position on spinel treatment is one line: spinel is rarely treated, though it might have fractures. Sapphire is not in that position. Heat treatment is routine across the sapphire trade, to the point that untreated material is the exception worth asking about, which is why we wrote a whole article on what to ask about sapphire heat treatment. If buying something that came out of the ground looking the way it looks is the thing you most want, spinel is an easier stone to get that from than sapphire is. We would rather say that than have you find it out later.
Red spinel takes its colour from chromium, the same trace element behind ruby, which is why the two were confused for centuries. The Black Prince's Ruby in the British Imperial Crown is a red spinel. The practical catch is size: the GIA notes that spinel is rare above five carats today, and fine rough is often cut to non-standard dimensions to save weight. Plan the design around the stone rather than the other way round.
Tourmaline Buys You Colour and Charges You in Toughness
No other gem material covers the colour range tourmaline does. The GIA lists its colour simply as all colours, and the copper-bearing Paraiba material from Brazil produces vivid blues and greens nothing else quite reproduces.
The price of that range is structural. Tourmaline runs 7 to 7.5 on the Mohs scale, which is respectable, but its toughness is rated only fair. Hardness and toughness are different properties, and fair toughness is the number that should shape your thinking. High heat can alter tourmaline's colour, and sudden temperature change can cause fracturing outright. Warm soapy water is the recommended cleaning method; ultrasonic and steam cleaners are not recommended for it at all.
Tourmaline is also strongly doubly refractive, with birefringence running from 0.018 to 0.040. In practice that means real pleochroism. Look at any tourmaline in the orientation it will sit in the ring, under ordinary daylight, not only under the display lighting where it was shown to you.
Treatment. Heating and irradiation are the two significant tourmaline treatments. The distinction between them is one you should care about: heat-induced colour is stable and undetectable, while colour produced by irradiation can fade with exposure to heat or bright light. Those are not equivalent purchases, and only one of them is a question you can resolve after the fact.
Zircon Has More Fire Than You Expect and Less Armour
First, the correction everyone needs: zircon is a natural mineral and has nothing to do with cubic zirconia, which is a manufactured diamond simulant. The names are an accident of chemistry that has cost zircon a great deal of reputation.
What zircon actually has is optics. Its refractive index reaches 1.925 to 1.984 in high-type material, with very high lustre and dispersion, and birefringence up to 0.059. The GIA describes the effect neatly: zircon's pronounced double refraction means you can see twice as many facets and twice as much fire. Put a well-cut blue zircon next to almost anything and it will out-sparkle it.
The trade-off is the hardest one on this page. Zircon runs 6 to 7.5 on the Mohs scale with fair to good toughness, and the GIA states plainly that zircon can be brittle and should be worn and stored in a way that avoids hard rubbing, and that it is not as hard or tough as a stone like sapphire. Facet edges are where you will see it first.
Two further things to know before you commit. Zircon is commonly heat-treated to produce blue and colourless varieties, and some heat-treated stones may revert towards their original light brown after prolonged exposure to bright light. And zircon sometimes contains traces of uranium, irradiating itself over geological time and altering its own properties, which is why its hardness is quoted as a range rather than a single figure. Ask which end of that range your stone sits at.
Questions Worth Putting to Whoever Is Selling You the Stone
These are the ones that change the answer, and a good seller will not need to check before replying.
- Has this stone been treated, and how? The useful answer names the process and says whether the result is permanent. For tourmaline, heated and irradiated are not the same answer.
- What is its toughness, not just its hardness? If the reply is only a Mohs number, the question has not been answered.
- Can I see it in daylight, away from the display lighting? A confident seller says yes immediately. This matters most for tourmaline and zircon.
- How should this stone be cleaned? If a stone should not go near an ultrasonic cleaner, you want to know that before it is set, not afterwards.
- How does the setting protect it? A stone with fair toughness or a brittle edge belongs in a design that accounts for it.
That last question is the one people skip. Durability is decided at the design stage, not managed later, and a bezel setting protects a vulnerable girdle in a way no amount of careful wearing can replicate.
What This Means in Practice
For a ring that gets worn every day without a second thought, spinel is the stone on this list we would back without hesitation, and on the treatment question it has a genuine advantage over the sapphires we sell. Tourmaline and zircon are remarkable materials, but both ask something of the person wearing them, and it is fairer to say so now than to let you discover it through a chipped facet in three years.
That is not an argument against either of them. It is an argument for matching the stone to the hand and the life it is going onto. If you want the colour only tourmaline gives, or the fire only zircon gives, buy it with your eyes open and design the ring around what it needs. If you would like to see any of them properly, in daylight, and work through what each would ask of the design, that is a conversation we are glad to have.
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Laher is a bespoke jewellery studio in Surry Hills, Sydney. We design and handcraft engagement rings and fine jewellery using Australian sapphires and unique coloured diamonds.