Diamonds are pure carbon arranged in a highly stable crystal lattice, granting them exceptional hardness. Their formation requires geological conditions of extreme heat and pressure, making natural diamonds inherently rare. This rarity, combined with their industrial and aesthetic value, drives a global search for the specific geographical locations where these crystals are found.
From Mantle to Surface: The Geology of Diamond Deposits
Diamond formation begins deep within the Earth, typically 90 to 125 miles beneath the surface, within the lithospheric mantle. Immense pressure and temperatures between 1,650 and 2,370 degrees Fahrenheit compress carbon atoms into the crystalline structure. This environment exists almost exclusively under ancient, stable continental interiors known as cratons.
The diamonds remain stable until specific volcanic activity forces them rapidly to the surface. This transport occurs through violent, deep-seated eruptions that create structures known as kimberlite and, less commonly, lamproite pipes. These pipes are columns of volcanic rock that extend from the mantle to the crust, acting as high-speed elevators for the diamonds.
The ascent must be extremely fast, taking only hours or days, to prevent the diamonds from converting back into graphite under lower surface pressures. These kimberlite and lamproite pipes represent the primary source of diamonds, where the crystals are still encased in their original host rock. Only a small fraction of these pipes contain diamonds in economically minable quantities.
Today’s Top Producing Nations
The largest current sources of diamonds are concentrated in a few nations, reflecting the scattered distribution of ancient cratonic rock formations. Russia is the world’s largest rough diamond producer by volume, extracting close to 42 million carats in 2022. This production comes primarily from vast kimberlite systems found in the remote Siberian region of Yakutia.
Botswana stands as the global leader in the value of its diamond production, despite producing less volume (24.8 million carats in 2022). The average quality of its diamonds results in a significantly higher total value than Russia’s output. Botswana’s output is dominated by large-scale mining operations focusing on high-quality stones from massive primary deposits.
Canada is also a major contributor, ranking as the third-largest producer by volume, mining over 16 million carats annually. The Canadian deposits, often located in the remote Northwest Territories, are primarily mined from large kimberlite structures. These three nations—Russia, Botswana, and Canada—account for the majority of the world’s rough diamond supply by weight.
Other significant producers include the Democratic Republic of Congo (DRC) and Angola. The DRC is a major source by volume, though much of its production comes from alluvial sources, resulting in a lower average value per carat. Angola is a high-value producer, ranking lower in volume but higher in total value than the DRC due to the quality of its finds. South Africa remains a producer, though its current output volume is much lower than the top-ranked nations.
Secondary Sources and Historical Discoveries
Diamond deposits are categorized as either primary (kimberlite and lamproite pipes) or secondary, which are formed by erosion. Secondary deposits, also called alluvial or placer deposits, form when diamonds are weathered out of their original host rock and transported by natural forces. Water, particularly in rivers and coastlines, carries these dense crystals and redeposits them in new locations, often far from the primary source.
Alluvial deposits tend to concentrate the highest quality stones because the mechanical processes of transport destroy weaker or more flawed diamonds. Historically, almost all diamonds came from these secondary sources before the discovery of major kimberlite pipes in the late 19th century. Early diamond production came from the ancient alluvial river systems of India.
Brazil also became a major historical producer after discoveries in the early 1700s, with most finds being placer deposits. In modern times, coastal regions, particularly along the west coast of Southern Africa in Namibia, exploit highly valuable marine and beach deposits. These offshore and shoreline deposits are formed by the long-term action of ocean currents and waves that have naturally sorted and concentrated diamonds eroded from inland pipes.