De Beers used “A Diamond Is Forever,” a slogan created by copywriter Frances Gerety. The line became powerful because it joined a physical property of diamond with an emotional promise about enduring love.
Gerety wrote the phrase in 1947 while working for N. W. Ayer & Son, De Beers’s advertising agency. De Beers had an interest in expanding diamond demand, especially in the engagement-ring market. Advertising presented diamonds as expected symbols of commitment and encouraged buyers to see them as valuable because they were permanent and emotionally meaningful.
The slogan is not a scientific statement that diamonds are indestructible. Diamonds are the hardest naturally occurring mineral on the Mohs scale, but they can chip, fracture or be damaged by strong impact. “Forever” functions as poetic advertising language and as a reference to the stone’s durability.
The campaign helped make diamond engagement rings a widely expected custom during the twentieth century. De Beers’s influence over diamond mining, distribution and marketing made its advertising unusually consequential. The phrase is still cited by advertising historians as a model of concise emotional branding.