In the late 1800s, the Oppenheimerfamily established a diamond monopoly with its company, De Beers. Around that time, Victorian culture was busy assigning abstract concepts to material objects. For instance, Kate Greenaway’s wildly popular The Language of Flowers (1885) ascribed a meaning to each specie and variety of flower. A yellow rose meant platonic love, for instance. Such assignations applied to stones as well, which sometimes increased a substance’s value.
The idea that diamonds represented "perfect love" evolved during the Victorian era but was reinforced with a vengeance by the market manipulation of De Beers.
In the 1930s, De Beers set out to establish social status for large diamonds through giving a number of starlets hefty stones, arranging for glamorous photo shoots, and script-doctoring Hollywood movies to include scenes of jewelry shopping. The tradition began to be manipulated more closely in one particular aspect–the act of giving. Those starlets told tales of being surprised by their large stones. Movie scenes featured a hero giving his gal a big rock and watching her eyes grow wide with joy. The diamond began to be injected into relationships between men and women as a reproducible act–a script for life, not just film–and an inseparable part of courtship and marriange. In 1947, De Beers’ ad agency came up with the massively successful slogan "A diamond is forever," which implied that diamonds don’t crack, break, or lose value. (They do.) The slogan became so entrenched that the only proper way to "dispose" of diamonds was to hand them down to a female descendant.
Other techniques De Beers used are familiar today; they sent representatives to high school home ec classes to teach girls about the value of diamonds and feed them romantic dreams. The diamond went from being a status symbol to an emotional one–love measured in carats.
Ten-year anniversary rings were created and heavily advertised in the 1960s after De Beers was forced to purchase large stocks of Russian diamonds. Most of these diamonds were small, white gems of less than one-quarter carat. As De Beers had been pushing engagement rings with larger (and mostly South African) stones, they had to adjust their campaigns. Hence the eternity ring–equally expensive but with smaller stones–was marketed specifically for anniversaries.
In 1967, De Beers contacted advertising agency J. Walter Thompson to popularize the diamond engagement ring in Brazil, Germany, and Japan. While De Beers found limited success in the former two countries, Japan far exceeded expectations. By 1978, half of all Japanese brides received a diamond engagement ring. By 1981, the number had grown to 60 percent; the "tradition" had taken hold. Just how did the J. Walter Thompson agency accomplish this? A basic but general ad campaign similar to that in the U.S.–the diamond ring was pitched not as a product but as a symbol.