Everything you need to know about choosing a diamond for your loved one.

Before 1930, few American men bought diamond engagement rings, and the ones they did buy were inexpensive and of low quality. Today, despite the diversification of proposals and the gestures that accompany them – especially for non-heterosexual couples – over three quarters of American brides are given engagement rings at an average cost of $4,000. How did this happen?

In his seminal 1982 story in The Atlantic, investigative journalist Mr Edward Jay Epstein described what he called the “diamond invention”, and the “creation of the idea that diamonds are rare and valuable, and are essential signs of esteem”. It was due to the discovery of massive diamond mines in South Africa in the 19th century, which flooded the global market with a surplus of diamonds, driving prices down.

The consortium that controlled these mines is now called De Beers, which successfully inflated the price and perceived value of diamonds with marketing and advertising. The link between love, diamonds and status was cooked up by an ad agency for a De Beers advert, when it created the masterpiece of copy writing: “A Diamond is Forever”. This promise of endless romance ensured many diamonds weren’t sold but kept as heirlooms. The maxim that a man should spend up to two months’ salary on an engagement ring was also from this piece of De Beers marketing: “How else could two months’ salary last forever?” When you buy an engagement ring you are participating in a piece of viral marketing, not a time-honored tradition.

This knowledge is not going to get you very far when asking someone to marry you. Gimlet-eyed realism is so very counter to the way we do marriage now. So, to ensure you don’t let it go to your head, we at MR PORTER decided to consult Mr Quig Bruning, a jewellery specialist at Sotheby’s, for his advice on the topic. He is responsible for appraising jewellery and advising clients on buying and selling at auction, and collaborates on all of Sotheby’s worldwide jewels sales, travelling frequently to meet with clients and promote auction highlights at exhibitions and events.

This is his top advice for buying an engagement ring.

“Everything is dictated by what you can afford,” says Mr Bruning. “I think the rule of spending two-three months of salary is outdated. It has to be a figure you feel comfortable with spending, and you have to be careful not to overstretch yourself. For me, what’s much more important is the emotion and feeling behind the purchase. What I can do is direct you to the best dealer and best price. For instance, I had a client who found a Blue Nile diamond online which would have cost $110,000, but I managed to help him get pretty much the same one from a dealer for $75,000. Everyone has to make the decision themselves about what they can afford to spend. And hopefully, it will be forever. It’s great to know that when my wife looks at hers, it reminds her of that time.”

“It could be something that’s specific and meaningful to you both as a couple. It doesn’t even have to be a diamond. I helped one man get a ring made from meteorite. Or it could be something that’s specific to her and something that she wants. Remember, she’ll be wearing it. I knew that my wife always loved sapphire diamonds. So be observant. Or you can make a judgement based on her style and aesthetic. Is she very trendy and fashionable? Or does she dress in a very understated and minimal style? Or is she colourful and flamboyant? For instance, if she dresses very classically, then you might want to go for something vintage. Another tip is to go to an auction house or museum with a great jewellery collection, and see which pieces she is drawn to.”

“The vast majority of rings consist of one main diamond, with perhaps, a couple of side stones. The four Cs (cut, clarity, carat, and colour) determine the value of a diamond. The bigger, rounder and clearer the diamond, the more expensive it will be. White diamonds are the most expensive. Once you have an idea of what’s important to you, then we can start to offset one against the other. For instance, if size is your main concern then you can perhaps compromise on clarity, and so on. Many diamonds have tiny flaws which can’t be seen by the naked, untrained eye, and these are much cheaper. However, beware, if you go somewhere and the deal sounds too good to be true, say someone is selling for $5,000 a diamond you saw online for $100,000, then it probably is.”

Keep up to date with The Daily by signing up to our weekly email roundup. Click here to update your email preferences