Engagement rings: The questions every buyer should consider

I'd like to surprise my fiancée with a ring. What do I do?

A surprise proposal coupled with the presentation of a beautiful ring from your pocket is very exciting. It's also a bit risky. You should know her preferences in terms of what kind of stone, type of setting, and colour of metal. 

Consider the design of other jewellery she loves, or ask her mother or close girlfriend for an idea of her preferences. However, shopping for a ring together is in itself a romantic exercise, and the safest way to make certain she loves it.

How can I determine her ring size?

If it's to be a surprise you need to be crafty: the best solution is always to have one of her rings measured by a jeweller. There can be up to a half finger-size difference between the left and right hands, which can be easily adjusted after you have given the ring.

Why are diamonds such a popular stone for engagements?

For excellent reasons: diamond is the hardest substance known to man and has more brilliance and fire than any other gemstone. It will withstand daily wear and look beautiful for decades. Having said this, a diamond can be damaged if knocked against a rock or marble surface, and it can be scratched by another diamond, which is why diamond jewellery should always be carried or stored individually in pouches.

What should I look out for in terms of setting?

The number of prongs and how they're constructed is very important. There should be four to six prongs securing the stone. Assess the durability of the prongs, especially on a pre-worn ring. If they are made of thin metal, it's not impossible for a claw to get caught on clothing and be bent backwards; if the ring only has four prongs, you could lose your stone.

If the ring is pre-worn, take it to a jeweller and make sure the setting is robust enough to withstand daily wear for many years.

What are the Four C's?

Colour, clarity, cut and carat weight, which are the standards for judging the quality of any diamond. Developed by the Gemological Institute of America (GIA) in 1953, the grading system is used throughout the world and is a trusted indication of quality.

Which of the Four C's is most important?

They're all to be considered together. You should closely compare different stones, and weigh factors such as size against colour and clarity. Remember this ring will be worn every day and doesn't have to be a top-rated D Flawless. With the naked eye, people can't identify a VVS1 diamond from a VS2, but the price can be significantly different.

What about a diamond certificate?

Always ask for a certificate and, if necessary, get advice to help you fully understand it. A certificate documents the vital statistics of a diamond, including its weight, colour and clarity, the proportions of the stone, the cut and polish, and whether it has fluorescence, which is generally not a plus point. It will also say if the diamond has graining.  

Christie's recommends and only uses GIA certificates. An old cut stone may not have a certificate, but one can usually be obtained in a few weeks. Certificates that are several years old may need to be updated in case the stone has been damaged since it was issued.

What is graining?

Graining is the stone's growth lines that are occasionally visible under magnification and can affect the stone's value by reducing its brilliance. If the certificate says the diamond has significant graining, in most cases you may want to choose another. 

What is the effect of fluorescence in a diamond?

It is not uncommon for diamonds to have a certain degree of fluorescence. The fluorescence is triggered by exposure to strong light, in particular direct sunlight, which can give the diamond a milky or lacklustre appearance. 

It depends on the colour of the stone — a small degree of fluorescence can make a slightly yellow diamond appear whiter. Depending on your budget, you might be able to buy a nice-looking diamond with slight fluorescence for a bit less. However, fluorescence in a high white diamond — for example a D or E colour — would reduce the stone’s value. 

Can a ring always be sized?

No. Certain rings, because of the design of their shoulders, may be difficult to size. An adjustment could put a strain on the settings so that they no longer do their job effectively, and the gemstones set in the shoulders of the ring could then pop out. Similarly, rings with stones all the way around the hoop cannot be sized.

What about a pre-worn ring?

You should carefully examine the overall quality and condition of a pre-worn ring, and particularly the settings of any precious stones. Look at the hoop, which may be worn at the back and require replacement. Make sure the ring can be sized, because even a slightly loose-fitting ring could be lost, commonly when trying on gloves in shops — if the glove is too small, the ring could come off in the glove without you even knowing!

Besides diamonds, which gemstones are popular for engagement rings?

Sapphires and rubies are both very popular engagement stones and their high degree of hardness, second only to diamonds, makes them durable for a lifetime. Emeralds are not as hard or as durable as sapphires, rubies and diamonds, however if they are set with a gold rubover setting this will greatly help to protect the emerald in the long term. 

Are some stones not ideal for engagement rings?

Opals may dry out and crack with daily wear and are better for occasional wear. Pearls, whether cultured or natural, can absorb liquids and stain. Cultured pearls usually have several microns of nacre — diamond-shaped crystals of calcium carbonate, also known as mother-of-pearl — on the surface, which will eventually erode and not look as good in five to 10 years. Overall, it’s best to avoid stones graded below 7 in hardness. 

What about gold versus platinum?

The decision to select a ring in yellow, white or pink gold versus platinum is a personal one. Platinum is slightly more dense, making it heavier than gold, and some people enjoy this more solid feel. Platinum will dull a bit with age but can be polished, while white gold brightens with wearing. Platinum is more ductile, and therefore it's often used in delicate settings.

Why do some antique rings look dull?

Rings dating from the 19th century were commonly crafted in yellow gold and silver, because it was easier to set gemstones in silver — a softer metal. One should never polish the setting of this style of antique ring, because it will remove the natural darkening of the silver and gold and diminish its value. 

If the ring has been polished when purchased, be aware that it will begin to dull within a few months. The patina of an old ring is part of its beauty.

What about rings from a certain period or maker?

Many people are fond of jewellery from a certain period, such as the 1920s, the 1950s or the 1970s, and may want to match their engagement ring with the period they prefer. Christie's auctions the finest jewellery from these eras, and our specialists can try to source a special piece for a client. 

Signed engagement rings from established jewellery houses such as Cartier, Graff, Harry Winston and Van Cleef & Arpels, among others, can often be purchased at our auctions and give an assurance of high quality stones and the finest workmanship. 

Why buy an engagement ring at auction?

Christie’s is an excellent place to find the right engagement ring. We offer a wide variety of new and pre-worn styles, with quality and value authenticated by our in-house experts. Christie's specialists will always be on hand to explain the differences between various stones and designs and to point out the considerations to be weighed.

At auction, buyers are advised to be more flexible and to go with a view to discovering a ring they'll love. The broader the parameters the easier it will be to find something. 

Previews allow clients to examine pieces carefully and to learn from the experts. If the buyer is looking for something more specific, our private sales service could be a good option.

What is the most popular choice for an engagement ring?

A round, brilliant-cut diamond, because it has the most brilliance and sparkle of all the various cuts and is particularly robust to last a lifetime!

If you're considering purchasing an engagement ring (prices from £1,500 to £1.5 million / $2,000 to $2 million), Christie's is the ideal place to begin. Our experts will happily explore gemstones and styles with you and answer all your questions. All catalogues can be viewed online at christies.com.