Geological Formation and Natural Occurrence
Diamonds form deep within the Earth’s mantle, at depths ranging from 90 to 120 miles (140 to 190 kilometers) below the surface. Extreme pressure, 45 to 60 kilobars, and high temperatures, 1,650 to 2,370 degrees Fahrenheit (900 to 1,300 degrees Celsius), are required for carbon atoms to crystallize into the dense, stable structure of a diamond. These conditions are found in ancient, stable parts of continental plates known as cratons.
Diamonds remain trapped within the mantle until geological processes bring them closer to the surface. This ascent occurs through rare volcanic eruptions that create narrow rock formations called kimberlite and lamproite pipes. These pipes act as conduits, carrying diamond-bearing rock from the mantle rapidly upwards, preventing the diamonds from reverting to graphite due to lower pressures and temperatures.
The global distribution of these primary diamond sources is limited. Economically significant kimberlite and lamproite pipes are found in regions such as Southern Africa, Siberia, Canada, Australia, and Brazil. The rarity of these geological structures, combined with the conditions needed for diamond formation and transport, contributes to the natural scarcity of diamonds in accessible locations.
Mining and Global Supply
Extracting diamonds from these natural deposits involves resource-intensive mining operations. Methods include open-pit mining for shallower deposits, underground mining for deeper kimberlite pipes, and alluvial mining to recover diamonds from riverbeds and ancient shorelines where they have been eroded and transported. Each method presents unique engineering and logistical challenges.
A significant hurdle in diamond mining is the vast amount of material that must be processed to yield a small quantity of diamonds. For instance, in some operations, it can take processing hundreds of tons of rock to recover just a single carat of rough diamond. This low yield rate makes the extraction process expensive and time-consuming, requiring substantial investment in heavy machinery, energy, and labor.
The global supply chain for diamonds is concentrated among a few major mining companies. These companies manage the extraction, sorting, cutting, and polishing processes, distributing them worldwide. While new diamond deposits are occasionally discovered, the rate of discovery of economically viable mines has slowed, and existing major mines are gradually depleting their reserves.
The Reality of Rarity and Modern Alternatives
The perception of diamonds as rare has been influenced by their geological scarcity, extraction challenges, and historical market dynamics. Natural diamonds form under rare conditions deep within the Earth and are difficult to bring to the surface. However, their market availability has also been shaped by supply management strategies. For decades, a dominant entity controlled a significant portion of the world’s rough diamond supply, meticulously releasing diamonds to maintain their perceived value.
This controlled supply contributed to the idea of rarity, even as new deposits were discovered and mined. The market’s stability and the narrative of scarcity helped solidify diamonds’ status as a symbol of enduring value. However, this traditional view of rarity is now being redefined by technological advancements.
Lab-grown diamonds, also known as synthetic diamonds, offer a modern alternative. These diamonds are produced in controlled laboratory environments using methods such as High-Pressure/High-Temperature (HPHT) or Chemical Vapor Deposition (CVD). HPHT mimics the natural formation process by subjecting carbon to intense pressure and heat, while CVD involves growing diamonds from a carbon-rich gas mixture.
The increasing availability of lab-grown diamonds impacts the concept of diamond scarcity and value. These alternatives possess the same physical, chemical, and optical properties as natural diamonds, but they can be produced more quickly and at a lower cost. Their emergence provides consumers with more choices and challenges the long-held notion that diamonds are exclusively rare due to natural geological limitations.