Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Diamond as a form of carbon is a tasteless, odourless, strong, brittle solid, colourless in pure form, a poor conductor of electricity, and insoluble in water.
Diamond has the highest hardness and thermal conductivity of any natural material, properties that are used in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.
Because the arrangement of atoms in diamond is extremely rigid, few types of impurity can contaminate it (two exceptions are boron and nitrogen). Small numbers of defects or impurities (about one per million of lattice atoms) can color a diamond blue (boron), yellow (nitrogen), brown (defects), green (radiation exposure), purple, pink, orange, or red. Diamond also has a very high refractive index
Billions of years ago, 100 miles (161 km) or more in the mantle of the earth, pressure, heat and carbon atoms converged, creating the first diamonds. Hidden for hundreds of millions of years, volcanic activity transported them to the earth’s surface in magma, forming kimberlite pipes in the process. As erosion freed some of the rough diamonds, they ended up in riverbeds and silt. Even into the 1800’s, the world’s diamonds were found and collected in the soil and gravel of riverbeds.
The discovery of a kimberlite pipe in South Africa in 1869 marks the beginning of the modern diamond era. With it came the development of mining operations producing tens of millions of carats of rough diamonds each year – that includes a major discovery in Botswana in 1967, as well as other areas of Africa, Australia, Brazil and the Northwest Territories of Canada.
However, the earth’s mantle isn’t the only source for diamonds. In 1954, General Electric began creating diamonds in a laboratory and the first gem-quality HPHT diamonds were grown in a laboratory in 1970, and first sold in 1984. Today, man-made diamonds have become more common and are more difficult to identify on your own without help from a reputable gemological laboratory. Synthetic diamonds can be grown from high-purity carbon under high pressures and temperatures or from hydrocarbon gases by chemical vapor deposition (CVD). Imitation diamonds can also be made out of materials such as cubic zirconia and silicon carbide. Natural, synthetic, and imitation diamonds are most commonly distinguished using optical techniques or thermal conductivity measurements.
As of 2023, the total global reserves of industrial diamonds amounted to an estimated 1.7 billion carats. At that point, Russia's diamond reserves were estimated to be approximately 860 million carats. Thus, the Russian diamond reserves are the largest worldwide. Almost half of the world’s mined diamonds are used for industrial purposes as rough diamonds. Industrial diamonds can be used in cutting, drilling, grinding, and polishing.
In 2023, India was the largest exporter of diamonds worldwide, amounting to a total value of 18.2 billion U.S. dollars. This compared to the nearly 17 billion U.S. dollars of diamonds exported by the United States that year, ranked second. Although India is the world's largest diamond exporter based on value, this is due to the fact that India is the world's largest diamond polishing nation, which it supplies through raw diamond imports, rather than having a high mine production of diamonds.
