Betrothal or engagement rings are not a new concept. Roman men gave betrothal rings, the annulus pronubus, to their future wife to be worn on the third finger of her left hand. They believed that the vein in that finger, the vena amoris, linked directly to the heart. The rings were usually plain, with maybe a simple motif or engraving, often showing clasped hands. This practice became incorporated into the marriage ceremony by the early Christians.
It was not always easy to distinguish whether a ring was a betrothal ring or a wedding ring but most of the former were made of metal, without gemstones. They were rings like the Fede ring, with clasped hands, and sometimes with hands carrying a heart, labelled Claddagh rings from the 17th century onwards, lover’s knot rings, or the Gimmel rings which came from the Renaissance period, and the Posey or Posy ring of the 12th to the 18th century. Often these rings were just simple gold bands with inscriptions or engravings but those like the Gimmel ring were much more ornate, with enamel and gemstones.
The first documented use of a diamond engagement ring appears to have been given by the Archduke Maximillian of Austria to his betrothed, Mary of Burgundy, in 1477. It was a ring with a top in the form of a M set with diamonds.
Gemset rings were certainly used as betrothal rings by the wealthy from the 14th century onwards. The gems, including diamonds, were often set in the shape of flowers, hearts, and bows. In the 19th century, Queen Victoria received an engagement ring shaped as a gold snake set with emeralds, rubies and diamonds. In the 1850s, half hoop rings set with pearls were popular as engagement rings. Diamonds were not common until about 1875, often in the form of half hoop or as gypsy style rings. Solitaire diamond rings began to appear as betrothal rings towards the end of the century, particularly as South African diamonds began to be available. This trend, though, was in France and England, and not so much in the rest of Europe. It was also at the end of the century that the word ‘engagement’ rather than betrothal was used.
Up until WWII, while diamond engagement rings were given, many other gemstones were used in engagement rings. Obviously, the wealthy could afford the best stones. Queen Alexander was given an acrostic engagement ring in 1862. The Queen Mother of the present British queen had a sapphire engagement ring. in around 1923 while the Duke of Windsor gave Wallis Simpson a large emerald ring in 1936. Ordinary people could only afford very small diamonds, if any at all. WWI and the Great Depression saw diamond sales sag, hence De Beers, which controlled the diamond market, paid for an advertising campaign in the US to encourage the sale of diamonds.
A key component of the advertising campaign was linking diamonds with love and marriage and also setting a price for what should be spent on an engagement ring. To achieve the former, the ad campaign had to target both the groom and the bride. Servicemen returning from WWII were a perfect group. To prove their love, the only engagement ring they could give would be a diamond ring. For the women, most of whom were still at home in the US, the advertising message was more around how famous women, like movie stars, were being given diamond rings by the partners so that was what they should aim for when their turn came. A price was provided of what to expect, namely, a ring that cost one month’s salary (later extended to be two month’s salary in the 1980s). An engagement ring had, just had, to be a diamond ring. Today, most ads for engagement rings still focus on the diamond engagement ring.