Diamonds, the epitome of elegance and timeless beauty, are formed deep within the Earth's crust under extreme conditions of pressure and temperature. These mesmerizing gemstones are brought to the surface by volcanic eruptions, embarking on a remarkable journey before they become the coveted treasures we admire today.
Formation of Diamond
Diamonds are created when carbon atoms are squeezed together at pressures around 50,000 times greater than those at the Earth's surface and temperatures of approximately 1,600Ā°C. This intense environment causes carbon atoms to bond with four other atoms, forming a crystalline structure. This extraordinary process occurs only at depths of more than 150 kilometers beneath the Earth's surface.
Diamonds are discovered in three primary types of deposits: alluvial gravels, glacial tills, and kimberlite pipes. Kimberlite is an ultrabasic volcanic rock that forms when magma intrudes into the Earth's crust, bringing diamonds and other minerals from the mantle to the surface. Kimberlite pipes, which can range in diameter from 75 meters to 1.5 kilometers, are the primary sources of diamonds and can also be found in dikes and sills that are only 1 to 4 meters wide.
Appearance of Diamond
Diamonds exhibit a remarkable variety in size, color, and purity. Typically composed of around 99.95% carbon, the remaining 0.05% consists of trace elements that influence their color and crystal shape. These variations contribute to the unique beauty of each diamond.
Diamonds are renowned for being the hardest naturally occurring mineral, topping the Mohs' Scale of Hardness with a value of 10. This incredible hardness makes diamonds the ultimate abrasive, a quality that is highly valued in industrial applications.
Diamond and graphite are both polymorphs of carbon, sharing the same chemical composition but exhibiting vastly different structures and properties. While diamond is hard, transparent, and an excellent electrical insulator, graphite is soft, opaque, and a good conductor of electricity. The distinct crystal structures of these two forms of carbon account for their contrasting characteristics.
Exceptional Properties of Diamond
Transparency: Diamonds are transparent over a larger range of wavelengths than any other substance, from the ultraviolet to the far infrared.
Thermal Conductivity: Diamonds conduct heat better than any other material, outperforming silver by a factor of five.
Melting Point: Diamonds have the highest melting point of any substance at 3820 degrees Kelvin.
Atomic Density: Diamond atoms are packed closer together than those of any other substance.
At surface temperatures and pressures, graphite is the stable form of carbon. Consequently, all diamonds at or near the Earth's surface are slowly undergoing a transformation into graphite. However, this reaction occurs at an exceedingly slow pace.
Chemical and Physical Characteristics
- Chemical Composition: C (elemental carbon)
- Hardness: 10
- Specific Gravity: 3.5
- Transparency: Transparent to translucent in rough crystals
- Color: Variable, ranging from pale yellows, browns, and greys to white, blue, black, reddish, greenish, and colorless
- Streak: White
- Luster: Adamantine to greasy
- Cleavage/Fracture: Perfect in four directions forming octahedrons; conchoidal fracture
- Crystal Habit: Prismatic, forming isometric shapes such as cubes and octahedrons
Diamonds are not just captivating gemstones, they are a testament to the incredible forces and processes at work deep within our planet. From their formation under extreme conditions to their remarkable properties and diverse appearances, diamonds continue to intrigue and fascinate both scientists and jewelers alike.Ā