A diamond and a moissanite can be very similar from across a jewellery counter, but the differences become more obvious when you get right up close. They have different physical characteristics and respond to light in distinctive ways. They also have different conventions for grading their quality.
When you’re considering an engagement ring or another item of jewellery for regular wear, it’s worth asking for more than a general impression of value. How does it react to being set in a ring and worn for years to come?
Diamond vs Moissanites Starts With the Material
Diamond vs moissanites is crystalline carbon, and natural diamonds and lab-created diamonds are both real diamonds, formed through geology or human intervention.
Moissanite is silicon carbide. The jewellery-grade material typically comes from labs, since natural moissanite is extremely rare.
This is important because moissanite should not be regarded as a specific type of diamond, though it shares some optical qualities with clear gem-quality diamonds.
Those considering moissanite can investigate lab grown diamonds with mined diamonds if they want to choose a real diamond, but origin is not the defining factor of a gemstone: a laboratory-grown diamond is still a diamond, and moissanite is still silicon carbide.
Their Sparkle Is Not Quite the Same
Brilliance often provides the first obvious difference.
Both can reflect a considerable amount of light, but moissanite has more dispersion than diamond: it has more “fire”, which means the rainbow reflections may be stronger, particularly with a moissanite in a pavé setting or under spotlights and bright sunlight.
Diamonds have a different balance of brilliance, fire and contrast, particularly when the cut is exceptional. A well-set diamond can have more definition in its sparkle than a moissanite, with less emphasis on the fire.
Both effects are perfectly acceptable, and buyers can choose whichever appeals to them more. Some people may prefer the stronger dispersion of a moissanite, and others may get the impression they want from a conventional diamond.
The larger the stone, the greater the difference becomes. A larger face-up size makes the moissanite’s dispersion easier to see.
Hardness Is Excellent in Both, but the Numbers Differ
Engagement rings get dropped, knocked against tables, doors and bags, and subjected to all manner of everyday hazards – so a stone’s scratch resistance is more important than it might seem.
Diamond scores 10/10 on the Mohs hardness scale, which means it’s highly scratch-resistant. Moissanite is also a durable gemstone, typically around 9.25/10 on the scale, and so both are suitable for regular wear in ring form.
Hardness is about resistance to scratches, though: it does not account for other types of damage, and so the setting still plays a role. A vulnerable edge or a small projecting tip in a pear-shaped or marquise-shaped diamond, for example, could be more prone to chipping than a round brilliant of the same carat weight.
A Side-by-Side Look at the Practical Differences
| Feature | Diamond | Moissanite |
|---|---|---|
| Composition | Carbon | Silicon carbide |
| Mohs hardness | 10 | Around 9.25 |
| Optical appearance | Balanced brilliance, fire and contrast | Strong brilliance with more pronounced rainbow fire |
| Jewellery suitability | Excellent for frequent wear | Excellent for frequent wear |
| Evaluation | Often sold with recognised diamond grading reports | Not graded using the diamond 4Cs in exactly the same way |
| Typical buying priority | Cut, colour, clarity, carat and grading | Dimensions, cut quality, colour appearance and visual character |
It’s also worth keeping in mind that trying to compare just 1 of these factors can give a misleading impression of how 2 stones will appear. A gemstone is judged as a whole in terms of how it reacts to light. Its cut, setting and proportions all contribute to this, as well as its size.
Carat Weight Can Create a Misleading Comparison
Diamond buyers are familiar with the idea of carat weight. This is the weight of the stone, not its diameter.
Moissanite has a different density to diamond, so although the 2 gemstones can have approximately the same diameter when viewed face-up, they will not necessarily have the same carat weight. Moissanite tends to be measured in millimetres rather than carats, or stated in terms of an equivalent diamond size.
If the appearance on the hand is important, it’s best to judge the stones on millimetres rather than carats.
This is especially relevant to oval stones, because 2 stones with a similar weight can have very different proportions if the length and/or depth of 1 is significantly greater than the other.
Setting Choice Can Change the Comparison
A gemstone mustn’t be judged out of context: if you’re going to buy a ring, consider it as a whole, rather than thinking of the stone in isolation.
A solitaire setting exposes more of the stone, and the individual qualities of a diamond or moissanite will shine through. It may be easier to see the difference in dispersion. A halo or pavé setting includes a number of smaller stones, and if the moissanite and diamond are in this configuration, it’s best to judge the combination of sparkle and colour in a number of situations to appreciate the differences.
A bezel setting covers more of the perimeter of the stone with metal than an open prong setting does, protecting vulnerable edges and providing a clean, defined shape, but it looks entirely different to an open setting.
The choice of precious metal can also affect the setting’s appearance. White gold or platinum tends to give a cooler appearance than yellow or rose gold, and the overall impression depends on the choice of setting as well as the stone.
Diamond Grading Requires Closer Attention
Diamonds have a comprehensive system of grading, which can be important when you’re looking for a larger stone, or if you want to ensure that the quality and appearance of a particular stone fits your expectations.
Established gemmological laboratories tend to put together a grading report that includes measurements, carat weight, colour, clarity and other relevant observations for a round brilliant or other cut diamond, depending on the laboratory.
Diamonds are not identical: a grading report is not a guarantee that similar grades will always look the same, but it can give you a good idea of the stone’s proportions and performance.
Moissanite is not necessarily subject to the same conventions, and while sellers can describe its clarity and so on, buyers should be aware that the terms used for moissanite grading are not necessarily the same as those used for a diamond laboratory grade.
What German Buyers Should Check Before Ordering
For online jewellery buyers in Germany, practical considerations can be just as important as the appearance of the gemstone: does the description give the diameter in millimetres? How is the ring size expressed? What precious metal and fineness has been specified? What documents come with the gemstone?
Ask about your options for resizing the ring before you purchase it, especially if the band is pavé-set or there are stones going significantly far up the shank, as some styles of setting leave very little room for manoeuvre if the ring needs to be adjusted to fit a different finger size.
Try to see the stone in more than 1 type of light if you can, because store lighting can affect the apparent colour and brilliance of a diamond, and moissanite can, like diamond, display dramatically different levels of sparkle in daylight or artificial light.
For a ring that is going to be worn frequently, consider it in its entirety: the security of the prongs holding the stone in place, the exposure of any vulnerable edges, the height of the stone above the band (which can affect how comfortable it is to wear in combination with a wedding band), and other details of the setting should also be taken into account.
