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Cape Diamond

When London jeweler and author Edwin Streeter published the fourth edition of his book “Precious Stones” in 1884, he devoted a chapter to the momentous diamond finds in South Africa that had begun in 1867. Not surprisingly, these stones, discovered in the British Cape Colony, quickly became known as “Cape diamonds.” By 1911, when W.R. Cattelle, a later London merchant of prominence, published his book, “The Diamond,” the term designated diamonds with a slight-to-pronounced yellowish cast. What’s more, indicated Perry Wagner in his 1914 book, “The Diamond Fields of Southern Africa,” “Cape” had been a color classification since at least the turn of the century.

Hence, for most of its life as trade jargon, the term “Cape” has served the purpose it did in the De Beers buying and sorting offices at Kimberley in the cartel’s early years: as pejorative shorthand for the presence of yellow in diamonds. Even today, the term conjures up an intrusive, value draining tinge of yellow in the mind of the diamond professional.

But while “Cape” has been synonymous with yellow for more than 90 years, its rapid transformation from an origin to a color term within 25 years of its appearance has never been explained. Indeed, many people are unaware that the word ever had a geographical context. Here’s why.

Code Word for Cartel

Many of those who entered the diamond trade in the post-war era assumed gemologists were responsible for the modern-day meaning of “Cape.” Actually they merely codified its exclusive usage as a color term. The man most instrumental for the enshrinement of “Cape” as a synonym for yellow in diamond lexicons was pioneering British gemologist Basil Anderson.

During extensive spectroscopic studies of yellowish and yellow diamonds, in the 1930s, Anderson noted a correlation between the strength of light absorption bands common to such stones in the blue and violet regions of the visible spectrum and the strength of color observed in them. To underscore this relationship, he dubbed these telltale patterns “Cape lines” in an article published in 1943. By the end of the decade, all diamonds with such absorption lines were known as “Cape series” stones. The term “Cape” had been stripped clean of all prior geographical meanings.

How could it have been otherwise for a gem with a single distribution channel: the De Beers diamond cartel? In March 1914, two decades before Anderson began his spectroscopic studies, the diamond came under centralized market control when the companies and governments involved in mining of this gem in South Africa and South West Africa (now Namibia) signed a pact that set, among other conditions, production quotas and rough valuation formulas. Although aborted by the outbreak of World War I, this agreement set the stage for subsequent pacts in 1919 and 1925 that forged De Beers as we now know it.

For all intents and purposes, the geographical origin of diamonds meant little or nothing to the jewelry trade by 1935. That was the year following De Beers’ formation of the Central Selling Organization, its vehicle for selling rough to regularly invited buyers in what are now known as “sights.” Few were aware of De Beers’ deft maneuverings to become the main buyer of diamond production from major sources not directly under its control. To the outside world, there was basically only one source for rough diamonds. De Beers. This is an important point to recall when discussing the lingering dominance of any diamond classification whose early use can be traced to De Beers. In short, the evolution of “Cape” into a color term is inseparable from the emergence of the De Beers cartel.

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Cape Diamond