How much you can afford to spend goes without saying, but there's also the ring recipient's own personal taste and her lifestyle - a giant rock may not be the wisest investment if it's going to impede her daily keyboard activities. It has to fit with her jogger-wearing, greasy hair days just as much as it does when she's glammed up.
"There's no denying that an engagement ring holds a very emotional and romantic significance for any woman who wears one. It's also an extension of their individual style and, to some extent, an expression of personality and taste," says Melvyn Kirtley, chief gemologist at Tiffany & Co. "In choosing a ring style, couples should think long term. The diamond will last a lifetime and the style of its setting should reflect the taste and personality of the wearer."
Engagement rings are not so trend-driven as fashion jewellery, but neither are they impervious to new directions. Black diamonds (rare stones known as 'fancy' when they occur naturally or 'carbonados' when they are man-made); stacked rings, and the intricate designs of the Edwardian era, are being touted as some of the hottest trends for 2017. The celebrity influence is also a powerful factor. When Prince William proposed to Kate Middleton with his mother's 18-carat sapphire engagement ring, this style soared in popularity. Now it's her sister Pippa's turn to be tastemaker. The art deco-inspired ring presented to her by hedge fund manager James Matthews cost an estimated €294,000, and enquiries to jewellers in the UK about asscher-cut diamonds (an octagonal shape with a deep cut, dating back to 1908), as seen on Pippa's ring, are reported to have increased dramatically.
"Jewellery has become a lot more prominent on the red carpet," says jeweller and engagement ring specialist Natasha Sherling, who creates bespoke pieces. "Maybe 10 years ago, actresses would have said they were wearing Prada, but now jewellery is as much a part of that.
"With Instagram, it's very easy to take a fabulous picture of your hand. Celebrities by their nature are quite wealthy people and they're quite showy people, so if you're going to see big diamonds on anybody, it's going to be them. You're seeing the best of the best so people are looking to them for a little bit of inspiration," says Natasha.
Yet for all that, certain principles about engagement ring purchasing remain. Diamonds, the toughest of all stones, are still the first choice and the durable platinum has continued to be the most popular metal. When looking at diamonds, the four Cs are essential: cut, referring to the stone's reflective qualities; clarity, as the less blemishes, the more valuable the diamond; carat, the diamond's weight but not actual size, and colour, with the closer the diamond is to colourless, the rarer it is, in a grading scale that goes from D to Z, and D, E and F being the most valuable.
Neville McDowell, jewellery manager at Weir & Sons, predicts that 2017 will see what he describes as "back to basics". "It's very much 'keep it simple'," he says. "We are selling an inordinate amount of simple, classic, reliable solitaire rings. Yellow gold sales are increasing, as well as rose gold, but from a very small base. They've gone up percentage wise quite a bit but sales are still being driven by platinum." Paul Brereton, manager at John Brereton Jewellers, agrees that yellow gold is on the up. "I would say that white gold is our number-one seller, and yellow gold has had 10 or 15 years of not being on the radar at all," he says. "Now it's 10 or 15pc, both in classic designs and more modern ones using yellow gold. Rose gold was popular for the last two years but yellow gold is beginning to take over from that now."
The halo setting (a large centre stone surrounded by smaller stones) has dominated the market in recent years, and is still going strong. However, Neville McDowell predicts that three and four-stone rings are set to rise in popularity. "These are things that we think will feature again, but these are all going to be small numbers in comparison to what we're mainly selling, which is the solitaire and the halo settings."
Natasha also believes that three-stone rings are set to make a massive comeback. "I think a lot of people might associate with their mothers, or even their grandmothers, but there has been a big resurgence in them in the last three to four years," she says. "I think it's because they're just really flattering on people's hands, to have that flash of diamonds across your finger.
"The stones are usually the same size or the centre might be slightly larger, but it's three good-sized stones rather than just being a little bit of detail on the shoulder. That's coming back in a big way and I think it's because people are looking at it with fresh eyes.
"Halos are still beautiful and contemporary but they're very much of a time and I can see in the next few years, they'll start to phase out to make way for something new again," adds the jeweller.
This year looks set to be the year for different shaped stones. "There's definitely a move towards what's traditionally called fancy shapes and a move away from round stones," says Paul. He is seeing increased interest in oval and cushion-shaped diamonds, and this is something that Gráinne Seoige is also witnessing. Seoige is the founder of Grace Diamonds, which specialises in custom design jewellery, specifically engagement rings, the diamonds sourced and certified from South Africa.
"A big trend we're seeing for 2017 is the cushion-cut diamonds where we can design fabulous pieces based on clients' preferences," she says. "Of course the single solitaire and the halos are also a big favourite among our customers. Other hugely popular choices are the diamond-encrusted twisted halos and coloured stones."
A caveat about coloured stones however: your choices are somewhat limited when it comes to engagement rings. Diamonds' enduring popularity is because they are the hardest stone known to man, followed by rubies and sapphires. Even if you have dreams of having your birthstone in your engagement ring, a lot of stones simply won't work because they won't withstand years and years of everyday wear. "If you have a larger gem stone like peridot, it will get scratched and when it's a larger stone you can see the scratches more easily, which irritates people," explains Paul.
"A lot of people have ideas about stones and they'd love an opal or pearl. We will sit them down and tell them that opals or pearls are not suitable for an engagement ring because they're not hard enough," says Neville. "An emerald is a beautiful stone but it's not suitable to be worn as an engagement ring, day in day out, unless you're going to do absolutely nothing with one hand. We'd be quite firm in pointing out that this is not practical, I know you saw a picture of it on somebody's hand, but it's far too high and flimsy a setting. It won't last."
One engagement ring phrase that needs to be part of every bride-to-be or ring purchaser's vocabulary is 'wed-fit'. If you choose a ring that is wed-fit, it means that the setting will fit neatly against it, with no gap. "If you look at the halo ring, it's not neat on the finger," explains Paul Brereton. "It's sometimes wider so we've designed it so a wedding ring will sit flush beside it and doesn't look out of place beside it. A lot of people will buy engagement rings and never really think that they have to buy a wedding ring with it."
Of course people are always finding new ways to show off their engagement rings. A strong Instagram trend has been to create a signature look by stacking, combining different metals and jewels on their fingers. "People love stacking. It's an excuse to wear more jewellery and obviously you have a trend now where people are getting lovely rings for promotions or for babies and to celebrate different things, and you only have so many fingers so it's nice to be able to stack rings," says Natasha.
"Having an eternity band as your engagement ring and pairing it with a much plainer wedding band is a very cool trend that's coming in. I love it because I just think it's a very elegant way to wear diamonds and it paves the way for stacking as well."
With this ring I thee promise
A rising pre-matrimonial trend in recent times is the popularity of promise rings, also known as a pre-engagement ring or a commitment ring. When somebody presents another with an engagement ring, there can be no doubt of the intent behind it. With a promise ring, it's not so clear-cut but generally it is assumed that it will be followed by an engagement ring. But getting a promise ring is not necessarily reflective of the ring purchaser's undecidedness about getting engaged; quite often it's because he or she is not confident about the big commitment of buying a ring that the other person might like. And it's not a new thing, promise rings date back to Roman times and during the Victorian and Edwardian eras, acrostic rings using a row of gemstones to secretly spell out words of affection - lapis, opal, violet amethyst and emerald to signify 'love' for example - were hugely popular.
These days, promise rings are more of a fashion piece. When compared to an engagement ring, the spend is considerably less, and there are no hard and fast rules as to what finger to wear it on, with some wearers even choosing to wear it on a chain around their neck. It all depends on the person, according to Paul Brereton of John Brereton Jewellers. "Some people go for a dress ring and then they move it along to the right hand when they get an engagement ring (engagement rings traditionally being worn on the left hand) or if it's just a silver ring, they normally keep it in a box as a memento." Jeweller Natasha Sherling designs a ring called From Here to Eternity which costs €140. "The reason I came up with mine is because I would imagine that whatever ring you're going to be proposed to with is always going to be very special and I knew that a lot of guys were going to the high street and buying token rings, but the problem is they turn your finger black and you end up binning it or putting it into a box," she says. "Mine are sterling silver and 9 carat gold so they're never going to tarnish and once you get the real thing, you can stack with that. An awful lot of my clients will get me to resize the promise ring when they get the real one so that they can wear it on their other hand."
Jewellery experts caution about managing expectations when it comes to promise rings. "The one piece of advice I'd always give is when you're buying a promise ring is, don't buy it with a huge big stone in the middle, because when they want the real thing, everyone is always a little bit let down," says Paul. Presenting somebody with a bling-tastic promise ring is a double-edged sword, agrees Neville McDowell of Weir & Sons. "I say to men, if you give this to your fiancée, do you realise that the real thing is €25,000-€30,000? Steer them towards a simple classic setting and design and invariably there's never a problem."
5 popular engagement ring styles
The most popular style of engagement ring, and consistently so. A centre stone dominates the ring with a setting of four to six prongs to keep it in place. Solitaires are simple and elegant, and are generally keenly priced. Picture: Natasha Sherling
Halos have enjoyed a huge level of popularity in recent years. They feature a small circle of stones around a larger centre piece, and this halo of stones is commonly diamonds although other precious gems can be used. They’re loved because they can make the centre stone look larger than it actually is. Picture: Weir & Son
Romantic and unusual, these take their cues from eras of that past and they can be vintage-style (i.e. new) or proper antique. Art deco is a perennially popular choice, notable for its straight lines and contrasting shapes and colours. Picture: John Brereton Jewellers
A style of ring set to make a comeback this year, the three-stone has a price advantage because the stones used are smaller than those in a solitaire for example, and it also allows greater choice because a variety of stones and shapes are possible. Picture: Weir & Son