Diamonds, known for their hardness and brilliance, are among the most sought-after gemstones globally. Their formation and discovery are intrinsically linked to specific geological conditions rarely found across Earth’s crust. Understanding where diamonds are found involves exploring their deep-earth origins, transport to the surface, and redistribution across various landscapes.
Deep Earth Origins
Diamonds primarily form deep within Earth’s mantle, 150-200 kilometers below the surface, beneath ancient, stable sections of continental crust known as cratons. These immense depths provide the extreme conditions necessary for carbon atoms to crystallize into diamonds. Temperatures typically range from 1,000 to 1,300 degrees Celsius, coupled with pressures between 50,000 and 70,000 atmospheres.
Carbon originates from primordial sources and recycled oceanic crust. Volcanic activity plays a crucial role in bringing these deeply formed diamonds closer to the surface. Magma rapidly ascends through conduits, forming kimberlite and lamproite pipes.
Kimberlite pipes are carrot-shaped structures that swiftly transport diamonds and other mantle rocks from great depths to the crust. Lamproite pipes are similar pathways. Only a small fraction of these pipes contain diamonds in viable quantities.
Diamonds in Riverbeds and Coastlines
Once diamonds reach the Earth’s surface, natural processes redistribute them, creating secondary deposits. Erosion breaks down the host rocks. Due to their exceptional hardness and resistance to weathering, diamonds endure this process.
Water in rivers and streams transports these diamonds downstream. Because diamonds are relatively dense, they tend to settle and accumulate in specific locations along riverbeds, forming alluvial deposits. These can be found in modern river channels or in ancient, now-dry river systems.
Furthermore, diamonds transported by rivers can eventually reach coastlines. Ocean waves and currents concentrate these diamonds along beaches and offshore areas, creating marine deposits. This phenomenon is particularly notable in regions where diamond-bearing rivers flow into the sea, with diamonds accumulating on continental shelves and in the surf zone.
Major Diamond Locations Worldwide
Diamond occurrences are globally distributed, with several countries standing out as major producers. Russia is currently the world’s leading producer by volume, with most of its diamonds originating from kimberlite pipes in the remote Siberian region of Yakutia, including the historic Mir and Udachny mines.
Botswana ranks as the second-largest producer by volume and the largest by value, owing to its high-quality gem diamonds found in large kimberlite pipe mines such as Orapa and Jwaneng. Canada has emerged as a significant producer, primarily from kimberlite pipe discoveries in the Northwest Territories, including the Ekati and Diavik mines.
Historically, South Africa was a dominant force, with early discoveries in alluvial deposits along rivers leading to the later identification of major kimberlite pipe mines like Kimberley and Premier. The country continues to produce diamonds from kimberlite, alluvial, and marine sources. Australia, particularly known for its rare pink diamonds, was a major producer from the Argyle lamproite mine in Western Australia, which ceased operations in 2020.
Other notable diamond-producing nations include Angola, which yields diamonds from both alluvial and kimberlite sources, and the Democratic Republic of Congo, where much of the production comes from artisanal alluvial mining. Namibia is prominent for its marine diamond deposits, concentrated along its coastline, with diamonds transported by the Orange River from inland sources.