Crystals of diamond are transparent, extremely hard and highly prized. But what makes them so special and so incredibly sought after?
In this week’s blog post, our Chemistry Content Creator Philippa is drilling down to discover the secrets of these famed jewels. Read on to find all the need-to-know facts on everything from their complex formation to their surprising uses.
What are the structure and properties of diamond?
Diamonds are made up of carbon atoms strongly bonded together by covalent bonds. Each carbon atom is bonded to four other carbon atoms in a tetrahedral arrangement. This gives diamond its unparalleled hardness and high melting point.
How are diamonds made?
Naturally occurring diamonds are forged in the crushing pressure and extreme heat of the Earth’s mantle, roughly 160 kilometers below the surface. Most of these were formed between 1 billion and 3 billion years ago when the planet was much hotter than it is today.
It’s extremely rare to find diamonds on the surface of the Earth, on account of the heat and high pressure conditions required to create them. However, very occasionally, surface diamonds can be created by asteroids crashing through the atmosphere and striking the ground where carbon is present. Diamonds have been found around the craters of asteroid sites such as the Popigai Crater in Siberia.
How are diamonds mined?
Because natural diamonds are most often found deep underground, a technique called mining is used to extract them.
- Marine diamond mining extracts diamonds from the ocean floor using special mining ships
- Alluvial diamond mining occurs in riverbeds and beaches, where thousands of years of erosion has washed diamonds onto the coastal sand and riverbed gravel
- Open-pit diamond mining is used closer to the earth’s surface, as miners remove the layers of sand and rock just above where volcanic activity has pushed diamonds upwards
Today, thanks to scientific advances, we don’t have to wait for billions of years for new diamonds to be produced and then spend billions of pounds extracting them.
Technology has allowed us to manufacture our own synthetic diamonds in labs, and there are a couple of different methods commonly used.
One popular method is plasma assisted chemical vapor deposition (CVD). This involves putting a substrate (a slither of diamond) in a sealed chamber with a carbon-rich gas and heating it to around 800°C. This allows the gases to adhere to the ‘seed’, and a diamond is eventually grown – carbon atom by carbon atom.
From earrings to x-rays: uses of diamonds
My reason for choosing diamonds is that, dense as they are, they represent the greatest worth in the smallest volume.
The rare properties of diamonds are what make them so useful and so valuable.
- Their special optical properties – which include a high index of light refraction and dispersion (sparkliness, in other words), and adamantine luster (shininess) – help make diamond one of the world’s most popular gemstones.
- The fact that diamonds are transparent, resistant to heat and incredibly durable makes them perfect for use in specialty lenses.
- Diamond ‘windows’ are used to cover openings in lasers, x-ray machines and vacuum chambers
- Diamond drill bits are used to penetrate glass, stone, ceramic, shell and very hard woods.
- Diamond’s strength makes it ideal to be used as speaker domes to enhance the performance of high quality speakers. This is because it can vibrate without deformation (which would degrade the sound quality).
- Diamond’s high thermal heat conductivity means it can be used as a heat sink, conducting heat away from heat sensitive parts of high performance microelectronics.
Can diamonds make us healthier?
No, you can’t put diamonds in a green smoothie, but they can be used in the diagnosis and treatment of some diseases.
Tiny diamond particles, nanodiamonds, that are a thousand times smaller than a human hair, can be used to treat cancer. They help deliver drugs to cancer cells, and because they are made of carbon, nanodiamonds have low toxicity and can remain in the body (rather than being pumped out before the drugs have had time to do their job).
Due to the remarkable relationship diamonds have with light, medical researchers have also considered using diamonds to treat blindness. Researchers are testing diamonds on eye implants as well as bionic eyes, so watch this space!
Did You Know?
- 80% of diamonds produced in labs go towards industrial use rather than being used in jewellery
- In ancient times, diamonds were seen as a sign of courage, invincibility and strength
- The ancient Romans and Greeks believed that diamonds were tears cried by the gods or splinters from falling stars, and Romans believed that Cupid’s arrows were tipped with diamonds (perhaps the earliest association between diamonds and romantic love)
- The Koh-i-Noor is one of the largest cut diamonds in the world, weighing 105.6 carats (21.12 g).It is part of the British Crown Jewels, and thought to be worth up to £400 million.
- It does rain diamonds, but only on Neptune and Uranus!
Learn more about diamonds (and get ready for your exams) with our teacher-written Revision Notes.
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