Nepedia
Back to Discover
Advanced Reader
🌍

Diamond

earth science Maturity 7-9 Next article →

A diamond is a solid form of the element carbon. Its atoms are arranged in a very specific crystal structure called diamond cubic.

Diamond structure
Diamond structure

This structure makes the diamond a tasteless, odorless, and strong solid. It is also very brittle, meaning it can break easily if struck. Diamonds are poor conductors of electricity, but they have the highest thermal conductivity of any natural material. This means they move heat very efficiently. Because of its unique atomic arrangement, diamond is the hardest natural material known to science.

Vickers anvil diamons
Vickers anvil diamons

The properties of a diamond come from its internal bonding. In a diamond, carbon atoms use sp3 orbital hybrids to form bonds.

Diamond structure
Diamond structure

This creates a tetrahedral shape where every atom is bound to four nearest neighbors. This arrangement is extremely rigid and creates a very high density. Natural diamonds have a density between 3150 and 3530 kilograms per cubic meter. This is over three times the density of water. This density is much higher than graphite, another form of carbon. In graphite, atoms form in planes that can easily slip past one another. In diamond, the bonds are so strong that the material is nearly incompressible.

Diamonds can appear in many different colors due to tiny imperfections. Most pure diamonds are colorless and insoluble in water. However, small numbers of defects or impurities can change their appearance. These impurities occur at a rate of about one per million lattice atoms. For example, boron can turn a diamond blue. Nitrogen can make a diamond appear yellow.

The Hope Diamond - SIA
The Hope Diamond - SIA

Other colors like green come from radiation exposure. Defects can also create brown, purple, pink, orange, or red stones.

National Museum of Natural History Gold Colored Diamonds
National Museum of Natural History Gold Colored Diamonds

Even the shape of the crystal can vary. They often occur as octahedra, which are eight-sided shapes, or as cuboidal crystals. Some unique types, like black carbonado, are made of fused diamond grains.

The history of diamond discovery is very long. The name comes from the Greek word *adamas*, meaning unbreakable or untamed.

Diamond face trigons scale
Diamond face trigons scale

Diamonds were likely first recognized and mined in India. They have been known in India for at least 3,000 to 6,000 years. They were used as religious icons and early engraving tools. In 1772, the French scientist Antoine Lavoisier proved diamonds are made of carbon. He used a lens to concentrate sunlight on a diamond in oxygen. He found that the only product was carbon dioxide. In 1797, Smithson Tennant showed that graphite is also made of carbon. This established that both are different forms of the same element.

Most natural diamonds formed deep within the Earth's mantle. They are typically between 1 billion and 3.5 billion years old.

Diamond age zones
Diamond age zones

At these great depths, high pressure and temperature allow carbon-containing fluids to dissolve minerals. These fluids then replace the minerals with diamonds. Eventually, volcanic eruptions carry these diamonds to the surface. They are deposited in igneous rocks known as kimberlites or lamproites.

VolcanicPipe
VolcanicPipe

Scientists can also create synthetic diamonds in laboratories. They use high pressures and temperatures or a process called chemical vapor deposition (CVD). CVD grows diamonds from hydrocarbon gases. Experts use optical techniques or thermal conductivity to tell natural stones from synthetic ones.

Because of their extreme hardness, diamonds are vital for industry. They are used to make cutting and polishing tools.

Diamond blade very macro
Diamond blade very macro

They are also used in the Vickers hardness test to measure other materials.

Vickers anvil diamons
Vickers anvil diamons

In jewelry, diamonds are popular because they resist scratching. This allows them to maintain a high polish for a long time. This is why they are often used in engagement or wedding rings. They also have a high refractive index and high optical dispersion. This means they bend and split light in a way that creates a bright sparkle.

Garnet inclusion in diamond
Garnet inclusion in diamond

Diamond science also connects to the study of our solar system. At ultra-high pressures and temperatures, diamond can melt into a metallic fluid.

Carbon-phase-diagramp
Carbon-phase-diagramp

These extreme conditions might exist inside the ice giant planets, Neptune and Uranus. Both planets contain about 10 percent carbon. They may even have oceans of liquid carbon. This metallic fluid could affect the magnetic fields of these planets. This might explain why their magnetic poles do not align with their geographic poles. Studying diamonds helps us understand both the deep Earth and the distant reaches of space.

704 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (26)
File:Diamant gisements.jpg
Diamant gisements.jpg
File:Carbon-phase-diagramp.svg
Carbon-phase-diagramp.svg
File:Diamond structure.gif
Diamond structure.gif
File:Diamond face trigons scale.jpg
Diamond face trigons scale.jpg
File:Vickers anvil diamons.jpg
Vickers anvil diamons.jpg
File:National Museum of Natural History Gold Colored Diamonds.JPG
National Museum of Natural History Gold...
File:The Hope Diamond - SIA.jpg
The Hope Diamond - SIA.jpg
File:Rough diamonds - necklace in UV and normal light B - composite.jpg
Rough diamonds - necklace in UV and...
File:World geologic provinces.jpg
World geologic provinces.jpg
Diavik Mine.tif
File:Eclogite, détail de la roche.jpg
Eclogite, détail de la roche.jpg
File:Garnet inclusion in diamond.jpg
Garnet inclusion in diamond.jpg

+ 14 more

More to explore

✨ What else?

Related topics you might enjoy

🔬 Go deeper

More advanced topics to explore

🪜 Step back

Simpler topics to build understanding

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.