Diamonds: A Look at the World’s Most Coveted and Hardest Natural Material

Diamonds, known for their unrivaled hardness and dazzling brilliance, are the most coveted gemstones in the world. Composed entirely of carbon atoms arranged in a crystal lattice, diamonds exhibit exceptional durability and optical properties.

Emerald Cut diamond with a finished weight of 142.90 carats
Emerald Cut diamond with a finished weight of 142.90 carats.
Discovered by Johannes Jacobus Jonker near Pretoria, South Africa on 17 January 1934 (image: Stan Celestian)

These precious stones range from completely colorless to various shades, including yellow, brown, and, more rarely, blue, green, pink, and red. The diamond’s high refractive index and dispersion give it a remarkable ability to reflect and refract light, resulting in the characteristic sparkle that it’s known for.

Formation and Occurrence

Diamonds form under extreme pressure and temperature conditions in the Earth’s mantle, typically at depths of 140 to 190 kilometers (87 to 118 miles). These conditions allow carbon atoms to bond in a tetrahedral arrangement, creating the diamond’s unique structure. Diamonds are brought to the surface through volcanic eruptions, where they are found in kimberlite and lamproite pipes, as well as in alluvial deposits formed by the erosion of primary sources.

Diamond in kimberlite (image: Stan Celestian)

Physical Properties

Diamonds are renowned for their exceptional hardness, brilliance, and fire (the dispersion of light into various colors). Their perfect octahedral cleavage can lead to clean and sharp facets when cut, which enhances their optical properties.

  • Chemical Formula: C
  • Crystal System: Isometric (Cubic)
  • Hardness: 10 on the Mohs scale (the hardest known natural material)
  • Specific Gravity: 3.52
  • Cleavage: Perfect in four directions (octahedral)
  • Fracture: Conchoidal
  • Luster: Adamantine (brilliant)
  • Transparency: Transparent to translucent

Varieties and Colors

Diamonds exhibit a range of colors, often graded by the GIA (Gemological Institute of America) scale from D (colorless) to Z (light yellow or brown). Fancy color diamonds, such as blue, pink, and green, are much rarer and highly valued. The color variations in these diamonds are typically due to trace elements or structural defects within the crystal lattice itself.

A variety of diamond crystals (image: Stan Celestian)

Notable Locations

  • South Africa: Renowned for its large and high-quality diamonds, particularly from the Kimberley and Cullinan mines.
  • Botswana: One of the world’s leading producers of gem-quality diamonds, including the Jwaneng and Orapa mines.
  • Russia: The Mirny and Udachnaya pipes in Siberia are significant sources of diamonds.
  • Australia: The Argyle mine is famous for its pink diamonds.
  • Canada: The Diavik and Ekati mines in the Northwest Territories are prominent producers of high-quality diamonds.

Uses and Significance

Diamonds are primarily used in jewelry, prized for their unmatched brilliance and durability. They symbolize wealth, power, and everlasting love, making them popular choices for engagement rings and other significant pieces. Beyond their aesthetic value, diamonds are also critical in industrial applications due to their hardness. They are used in cutting, grinding, and drilling tools, as well as in high-performance bearings and heat sinks.

Care and Maintenance

Despite their hardness, diamonds can be chipped or damaged by sharp impacts. It is essential to store them separately from other gemstones and jewelry to prevent scratching. Regular cleaning with a soft brush, mild detergent, and warm water helps maintain their sparkle. Ultrasonic cleaners can be used for a more thorough cleaning, but caution is advised with certain settings and types of inclusions.

Identification Tips

  • Hardness Test: Diamonds will scratch all other materials but cannot be scratched by any other substance.
  • Refractive Index: Diamonds have a high refractive index (2.42), contributing to their brilliance.
  • Thermal Conductivity: Diamonds conduct heat exceptionally well, distinguishing them from most simulants.
  • UV Fluorescence: Many diamonds fluoresce under ultraviolet light, typically showing a blue glow.

Diamonds continue to captivate and inspire, representing the pinnacle of natural beauty and enduring strength. Whether set in exquisite jewelry or employed in cutting-edge technology, their allure remains timeless and unmatched.

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