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What Is The Difference Between Diamonds And Coal?

What Is The Difference Between Diamonds And Coal?

People have been intrigued by diamonds since ancient times. These gemstones have always been in demand. Interestingly enough, people have made this whole diamond enigma even more inviting by adding coal to the equation. 

We’ve all heard coal and diamonds being mentioned in the same sentence, but: What is the difference between diamonds and coal?

Obviously, these two geological specimens are different in their looks and hardness. Price and sites of formation are on the long list of differences, too.

In this article, we’ve covered everything you need to know about coal and how it differs from diamonds. Ready to dive in and hear all about it?

What Is Coal? 

Coal is a black sedimentary rock that can be burned for fuel which is used to generate electricity. It’s composed primarily out of carbon and hydrocarbons, which contain energy. 

That energy can be released through burning, also known as combustion.

Coal is the most significant source of energy for producing electricity in the world and is created from the remains of ancient organisms. It’s considered a nonrenewable resource because coal takes millions of years to form, and it’s available in limited amounts. 

The formation of coal started about 300 million years ago.

Coal exists in underground formations called coal beds or coal seams. A coal bed can be about 98 feet thick and over 4,900 feet wide. Coal seams are found on every continent, but the most significant reserves are in the US, Russia, China, Australia, and India.

Coal is different from mineral rocks, which are made of inorganic material. You see, coal is made of plant matter – and it undergoes several changes before it becomes the black substance commonly burned as fuel.

Over millions of years, coal goes through different phases of carbonization and can be found at all stages of development.

Coal is generally ranked according to how much it changed over time. 

In fact, Hilt’s Law states that the deeper the coal bed is, the higher the rank it has. The material encounters higher temperatures and pressure at greater depths, and more plant debris is transformed into carbon.

Types of coal are:

  • Peat
  • Lignite
  • Sub-bituminous coal
  • Bituminous coal
  • Anthracite
  • Graphite

How Is Coal Used?

Coal has been used to heat homes and cook food for thousands of years now. For example, it was used in the Roman empire to heat public baths, and surprisingly enough, these black rocks were used for ornaments in the Aztec empire.

The entire industrial revolution was powered by coal as it was cheaper than wooden fuel and produced more energy when burned. Coal provided the power to mass-produce items, generate electricity, and fuel trains and steamships necessary for the transportation. 

Today, coal is still used for heating and producing electricity. Even more so, it is essential for the steel industry. 

Coal is the leading energy choice for most developing countries, too – and worldwide, coal consumption has increased by more than 30% in 2011 alone.

Coal can be used by individual households or in industrial furnaces. It produces heat for stability and comfort, as well as heating water for health and sanitation. 

In short, coal plays a significant role in modern-day living as we know it. 

Coal-fired power plants are among the most popular ways to generate and distribute electricity. In these plants, coal is combusted to heat the water in huge boilers. The boiling water creates steam – which turns the turbines and activates a generator to produce electricity. 

Simple, huh?

As we already mentioned, coal plays a role in the steel industry, too. Iron ore must be heated in order to separate the iron from other minerals and produce steel. 

Coal was used to heat and separate the ore, but it released impurities that made metal weak. 

So, scientists discovered a way to remove these impurities from coal before burning it. As a result, they got a material called coke which has fewer impurities and higher carbon content.

Coke is burned in the so-called blast furnace with iron ore and air. The hot air ignites the coke, and it melts the iron and separates the impurities. The resulting material is steel. 

Coking coal provides chemical properties that give steel strength and flexibility. The gases that are released during this coke-making process are used as a source of power. 

Coal gas is used for light and heat, for example. Coal can also be used to create syngas, a combination of carbon monoxide and hydrogen. Syngas is used as a transportation fuel similar to diesel and petroleum.

Coal & Carbon Emissions

Burning coal releases gases and particles harmful to the environment – carbon dioxide is the primary emission.

Carbon dioxide is, in a way, an essential part of the Earth’s atmosphere. It’s one of the so-called greenhouse gases that absorb and retain heat in the atmosphere, keeping our planet at a livable temperature. 

But “too much of a good thing” seems to apply to greenhouse gases. 

When coal – and other fossil fuels – are extracted and burned, they release concealed carbon into the atmosphere, leading to a significant build-up of greenhouse gases and affecting global climate and ecosystems. 

Nitrogen oxides and sulfur dioxide are also released when coal is burned. These substances are known contributors to acid rains, smog, and respiratory diseases. 

Fly ash and bottom ash are also a part of coal combustion. Depending on the coal’s composition, these particles can contain toxic elements such as cadmium, silicon dioxide, calcium oxide, and arsenic.

Under the proper heat, ventilation, and pressure conditions, coal seams can self-ignite and combust underground. Wildfires and lightning can also ignite any exposed sections of the coal seam.

These coal fires emit tons of greenhouse gases into the Earth’s atmosphere. 

To make matters worse, even if the surface fire is extinguished, the coal can smolder for years before flaring up and starting a wildfire once again.

Coal fires can also begin in mines due to an explosion. Once coal catches fire and starts smoldering, it becomes challenging to extinguish.

Learn More: Does Coal Become Diamond?

Pros & Cons Of Coal

Coal is a dominant part of the world energy budget. It’s relatively cheap to locate and extract and can be found all over the world. And unlike many renewable resources, coal production isn’t dependent on the weather. 

Coal can be produced 24 hours a day, seven days a week, 365 days a year.

People use and depend on many things that coal provides, including electrical power to our homes, schools, hospitals, and industries, as well as heat. Steel, crucial for the construction of buildings, relies on coke coal. 

Even coal byproducts can be used to make transportation fuels.

Coal mining provides economic stability for millions of people around the globe. The coal mining industry relies on people with a wide range of skills and knowledge.  

Coal is an industry that is crucial for countries in both the developed and developing worlds.

On the other hand, coal is nonrenewable energy. It took millions of years to form – and a finite amount of it exists on Earth. So, even though it’s a consistent and reliable energy source at this point, it won’t be available forever.

Also, mining for coal has to be one of the most dangerous jobs in the world. The health hazards to miners include respiratory diseases in which coal dust builds up in the lungs. Additionally, thousands of miners die every year in mine collapses, explosions, and other accidents.

Even more so, surface mining permanently alters the landscape. 

In mountaintop removal, the landscape is obliterated, and ecosystems are devastated. That leads to increased erosion in the surrounding landscape. Floods – and other natural hazards – put these areas at more significant risk.

Burning coal for energy releases greenhouse gases and toxins, such as carbon dioxide. These substances have an immediate impact on the local air quality and contribute to global warming.

Coal mining could impact local water supplies in several ways, too. Streams may be blocked, which increases the chances of flooding. Also, toxins can leach into groundwater, streams, and aquifers.

Coal is one of the most controversial sources of energy in the world. The advantages of coal mining are socially and economically significant – but mining devastates the environment in the process. 

Let’s Talk About Carbon

During the 20th century, when studies on the microscopic structural arrangement of the elements and materials commenced, the world came to know that diamonds and coal are made of carbon. 

That is the main reason behind this widespread misconception that diamonds are a refined, enhanced, and extravagant form of coal. 

The fact that carbon is the most common “ingredient” of these elements also made its way into famous quotes, like: “A diamond is a lump of coal that did well under pressure.” 

These adages might inspire some to handle their stress better – but scientifically speaking? There’s no truth in the assertion that coal is converted into diamonds with more time and under extreme pressure.

Continuous but usually unintended spread of false information has led many to believe that coal and diamonds are distant brothers from the same carbon father – or that coal is nothing but the premature form of the diamond. 

Why Are Coal And Diamonds Discussed Together?

It seems that innate human tendencies are responsible for this association. There is a considerable disparity between diamonds and coal’s uses, worth, and general social discernment. 

As we already explained, coal is an industrial mineral used to produce energy with no aesthetic value. On the other hand, diamond is an elite stone, and we think it has become redundant to talk about its aesthetic features.

When it comes to these geological specimens, let’s illustrate a scenario. 

Without any permission, you can easily pick up a piece or two of coal without anyone batting an eye. In contrast, one might have to plan an entire heist to get the same amount of diamonds in a similar manner.

Amid all these distinctly different realities of the two specimens, the thought that diamonds and coal are actually the same feeds people’s fascination.

The Site Of Formation

Coal and diamonds are formed at different locations beneath Earth’s surface. 

Precious stones are formed from carbon and its derivatives, around 100 miles – or more – beneath the ground. On the other hand, coal formation takes place closer to the surface. Even a “deep” coal mining site is only as deep as two to three miles into the ground.

Furthermore, their excavations suggest that they’re different geological specimens. Most coal mining is performed at the exact location where this sediment rock is naturally formed – but that’s not the case with diamond mining. 

Miners don’t dig 100-mile deep trenches to excavate diamond deposits. The mined diamonds are the ones that come close to the surface of the Earth from their original sites of formation during volcanic eruptions.

Read Also: What Do Diamonds Look Like When They Are Found?

The Form Of Carbon 

Coal and diamonds are derived from carbon, but this doesn’t mean a similar carbon composition is used to form these two; far from it. Diamonds are made from pure carbon deposits. That’s one of the reasons behind the clarity of these precious stones.

Meanwhile, the carbon used to form coal is packed with impurities we talked about before. These impurities are the reason why coal burning leads to greenhouse emissions.

The carbon used in the formation of diamonds sometimes contains a small amount of these impurities – but that doesn’t affect the basic structure and appearance of the stone. Different natural shades and color hues in some diamonds might be present, though.

Even more so, the sources of carbon are pretty different in both cases. Diamonds are made from carbon that’s present in the Earth’s crust. On the other hand, the majority of the coal deposits are formed from the carbon present in decomposed plants. 

Temperature And Pressure Treatment

The components required in the process of formation are also different for these two specimens. 

Carbon will start turning into a diamond under extreme pressure and temperature conditions found within our planet’s mantle. The heat and pressure treatment is then followed by a long cooling process that develops the hardness of the diamond

Coal forming also involves pressure and temperature changes – but they are nowhere near the extreme conditions of a diamond’s formation. 


So, once again, what is the difference between diamonds and coal?

  • Apart from the more than evident difference in hardness and color, other factors separate diamonds from coal. The price difference between these two carbon specimens is enormous, for example.
  • Even more so, diamonds are formed out of purest carbon, whereas coal is made of carbon present in decomposed plants. The heat and pressure are far more significant in the formation of diamonds than in coal, too. 
  • The site of formation is also different. Diamonds are formed at about 100 miles beneath the surface, while coal is generally created only a few miles underground.

See Also: Are Black Diamonds Just Coal?