The answer is diamond, and it was the minority choice. Of eight birthstone lists tabulated in 1913 by one gem authority, sapphire appears at April in seven and diamond in two, one list naming both. The American trade had adopted diamond the year before.
Two commercial decisions gave April its stone and made it the most recognisable name on the calendar. The first was taken in August 1912, when the American National Retail Jewelers’ Association adopted a standard list of birth-month stones for the jewellery trade. The second was an advertising contract signed in December 1938, whose paperwork now sits in a museum archive in Washington.
A standard list turns twelve loose associations into twelve lines a shop assistant can read off a card, which means a customer walking in on a January afternoon gets the same answer in Boston as in Denver. Whatever else it did, it made the birthstone sellable at counter speed.
Between those two dates the leading gem authority in the United States wrote a book arguing that the diamond should be taken off the birthstone calendar altogether.
The choice that was available
George Frederick Kunz published The Curious Lore of Precious Stones in 1913, the year after the trade list appeared, and in it he set eight historical birthstone lists side by side and counted which stones appeared in each month.
His April row reads: “Sapphire 7, diamond 2.”
Sapphire appears at April in seven of the eight, diamond in two, with one list naming both. One of the two diamond entries is not an old list at all but Kunz’s own composite covering the fifteenth to twentieth centuries. Whatever tradition means here, sapphire had a good deal more of it for April, and his September row runs the same way: chrysolite 6, sardonyx 2.
The list adopted in 1912 gives April diamond and September sapphire.
A tally like that has to be read for what it is. Kunz counted lists, not centuries, and lists copy from one another, so eight of them are not eight independent votes. He also chose which eight to include. The count establishes something narrower and still useful. For whoever compiled the sources Kunz had in front of him, sapphire was the April answer, and a jeweller in 1911 reaching for the traditional stone would have reached for it.
What Kunz proposed instead
His proposal went further than restoring sapphire. He wanted the winner taken off the calendar.
“As the diamond does not appear to have been known to the ancients and is not given in any of the lists of birth-stones before the last century, and as diamonds, like gold and platinum, may easily be used as accessories to other stones, would it not perhaps be better to omit the diamond from the list of the stones of the months, and rather use these gems as a bordering or other ornate addition to the stone of the month?”
That is a proposal to demote April’s stone to a setting material. His own table sits slightly awkwardly beside that sentence. Two of the eight lists he tabulated do give diamond to April, one of them a Polish list and the other his own composite. He qualified the claim with “before the last century”, so the two need not contradict him outright, and he does not stop to reconcile them.
His general objection is broader and better aimed. “Once we allow the spirit of commercialism pure and simple to dictate the choice of such stones, according to the momentary interest of dealers, there is grave danger that the only true incentive to acquire birth-stones will be weakened and people will lose interest in them.”
He was writing about a list drawn up by retailers, in the year after they drew it up, and he lost. April’s line has read diamond ever since.
The second decision
The N.W. Ayer Advertising Agency Records at the Smithsonian’s National Museum of American History include, among the legal papers, a folder of advertising service agreements for De Beers dated from 1938. The earliest De Beers proof sheets in the collection are from 1939. That is the paper trail of an account opening.
Jennifer Pequignot, whose 2019 doctoral study works directly from that collection, dates the start precisely: “In December 1938, De Beers and N.W. Ayer agreed to a ten thousand dollar contract to conduct marketing research and begin a nationwide advertising campaign in the United States.” The research came back saying Americans associated diamonds with love more closely than with anything else, and the campaign was built on that finding.
It is unusual to be able to say that much. Most advertising leaves only the advertisements, and the reasoning behind them goes into a bin when the account closes. Ayer’s did not. The agency’s records went to a national museum, so the internal memoranda and the research reports behind a campaign that ran for decades are catalogued and open to anyone who asks. The campaign that shaped April’s stone can be read from the inside.
The line that carried it came later. The Smithsonian’s own finding aid for the collection states that “The ‘A Diamond is Forever’ tagline was written in 1949 by Frances Gerety, a woman copywriter at Ayer from 1943 to 1970”, and adds that “In 1999, Ad Age magazine cited ‘A Diamond is Forever’ as the most memorable advertising slogan of the twentieth century.” The year is not settled. An item in the same collection is catalogued as an advertisement from the campaign, circa 1947, and Pequignot gives 1947 on the strength of Gerety’s own recorded interview, which is held in that collection. The Smithsonian’s prose and the Smithsonian’s catalogue do not agree, and the date gets quoted elsewhere with a confidence neither supports.
Whether the campaign invented anything
The sources pull in two directions. The dissertation’s own title calls the campaign the creation of the tradition, and its text says that before 1939 the giving of diamond engagement rings “was an unestablished practice in American culture”, and that what followed was “the direct result of thirteen years of strategic advertising and marketing campaigns”. Against that, the survey Ayer itself commissioned in 1938 and 1939 found that less than two thirds of the women asked owned a diamond engagement ring, and the dissertation files that result among the ones Ayer found troubling, alongside the finding that the women surveyed would sooner have had a car or a trip abroad.
Read together they describe a practice that existed and was not thriving. The campaign took a weak habit and spent decades tying it to one durable idea.
A figure circulates saying that, in Western countries, ten per cent of engagement rings held a diamond before the Second World War and eighty per cent by the end of the century. The trail runs back through a 2015 economics paper, which cites a 2014 BBC feature, which states it flatly and cites nobody. The agency’s own internal numbers, quoted in the same doctoral study, are duller and better attested. A memo of May 1952 put diamond engagement rings at nearly eighty-five per cent of American marriages that year. A survey for Ayer in 1988 found eighty-one per cent of first-time brides receiving one, up eight points on 1980, which means the figure dipped in between and recovered. Neither number describes a steady climb.
The idea was well chosen, and the choosing shows. An engagement ring has to do something no other purchase does, which is stand for a decision nobody intends to revisit. Almost any gem is pretty. The hardest natural substance there is can carry an argument about permanence without the argument sounding like a claim. That reading is mine rather than the archive’s, though the slogan’s own wording is hard to take any other way.
One consequence is peculiar to April. For most months the birthstone is the reason a reader has come looking at all. For April the stone was already in the room, attached to a quite different occasion, before anyone mentioned birthdays.
April’s stone is therefore where it is because a retailers’ association preferred it to sapphire, and it is known everywhere because N.W. Ayer, in Philadelphia, spent decades attaching it to one word.
Carbon, and a very old name
The Handbook of Mineralogy is brief about it. Diamond is “Nearly pure carbon”, cubic, with cleavage “{111}, perfect” and hardness 10, and its occurrence note names kimberlite and lamproite as the rocks that carry it. GIA puts the formation depth at 150 to 700 kilometres and describes the kimberlite eruption as the transport rather than the cause, with the diamonds along for the ride.
The name is older than any of the commerce. The Handbook glosses it as “A corruption of the Greek for invincible”. Whether the ancients using that Greek word meant diamond is a separate question, and Kunz answers it in the same chapter. Discussing a second-century poem in praise of adamas, he writes: “This probably refers either to colorless corundum, the so-called ‘white sapphire,’ or to quartz. The writer is disinclined to believe that the ancients knew the diamond.”
Sapphire is the stone that was there before, on seven of the eight lists Kunz counted, and it is on the calendar now under September. Anyone curious about what April’s line used to say can look the stone up in the Crystalance Mineral Library and judge the trade’s choice for themselves. Kunz got his objection into print the year after the association adopted the list, which is about as fast as a book can be written, and April’s line has read diamond for over a century since.
Sources
- George Frederick Kunz, The Curious Lore of Precious Stones, 1913, chapter IX, for the eight lists, the April tally, the proposal to omit the diamond and the objection to commercialism: gutenberg.org
- Smithsonian National Museum of American History, N.W. Ayer Advertising Agency Records, NMAH.AC.0059, finding aid, for the De Beers agreements from 1938, the 1939 proof sheets and the 1949 attribution of the tagline: sova.si.edu
- Jennifer Lynn Pequignot, Why a Diamond Means Forever: The Creation of the Diamond Engagement Ring Tradition in the United States, 1939-1996, PhD dissertation, Auburn University, 2019, for the December 1938 contract, the survey findings and the Ayer internal figures: etd.auburn.edu
- Francis, Andrew M., and Hugo M. Mialon, “‘A Diamond Is Forever’ and Other Fairy Tales”, working-paper version of the 2015 Economic Inquiry article, where the ten to eighty per cent figure appears and is credited to a news feature: csus.edu
- The Jewelers’ Circular and the Horological Review, 14 August 1912, reporting the adoption of the standard list: archive.org
- Handbook of Mineralogy, diamond: handbookofmineralogy.org
- GIA, “Kimberlites: Earth’s diamond delivery system”, Gems & Gemology, Summer 2019: gia.edu
