Unveiling the Truth: How Diamonds are Really Formed

Are Diamonds Made from Coal?

You might think that diamonds are old pieces of coal transformed by high pressure and temperature, right? Incorrect! This is a myth, akin to the idea that one more drink will cure a hangover or that being out in the cold causes a cold. Diamonds actually preceded plants, which are essential for coal formation.

The traditional recipe for a diamond includes: carbon deposits deep within the Earth, exposed to high temperatures and pressures.

The exact duration for diamond formation is unknown; it could be days, weeks, months, or even millions of years. Most diamonds are hundreds of millions of years old, with many dating back 1 to 3 billion years. Diamond growth isn’t always continuous. Sometimes the growth halts due to changes in temperature or pressure and can resume after millions of years.

Determining the age of a diamond is complex. While a diamond itself can’t be dated precisely, inclusions of other minerals within it can provide estimates, especially with elements like potassium undergoing radioactive dating.

As diamonds form deep within the Earth, they encounter various gases, minerals, and materials around them. Although they become incredibly hard, their color can be affected by what they come in contact with during formation. Most diamonds appear white but may show a yellow or light brown tint on closer inspection. This variation doesn’t mean the diamonds are flawed; it just highlights their unique beauty.

Diamond Formation

How do diamonds actually form? There are four primary ways. We’ll explain each below, but you can also refer to the image below for a visual representation.

Diamond Formation in the Earth’s Mantle

Most diamonds found in commercial mines were formed approximately 150 kilometers below the Earth’s crust, in a region of the upper mantle known as the “diamond stability zone.” This region has conditions of over 1,000 degrees Celsius and high pressure. Here, diamonds continuously form and grow over billions of years. They are brought to the Earth’s surface during seismic events like volcanic eruptions, embedded in rocks known as xenoliths.

Diamond Formation in Subduction Zones

Diamonds can also form in “subduction zones,” areas where tectonic plates converge, causing one to move under the other. Some research indicates that subducted seawater might play a role in diamond creation in these zones; other studies have found diamonds containing tiny bits of oceanic crust.

Diamond Formation at Impact Sites

Surprisingly, some diamonds are believed to originate from asteroid impacts. Such impacts create extreme temperatures and pressures. Diamonds have been found in meteor craters in Arizona and Siberia, Russia, where excavations at the Popigai Crater have uncovered diamonds up to 13 millimeters in size.

Diamond Formation in Space

Captivatingly, scientists at NASA have discovered minuscule diamonds in extraterrestrial bodies. These diamonds may form either in outer space or in the mantles of other planets.

Lab-Made Diamonds

Technology has advanced, including in the creation of diamonds. Lab-grown diamonds are gaining popularity. These diamonds look and feel the same as natural ones because the growing process mimics the carbon-atom formations created by Mother Nature.

In a lab, technicians induce diamond growth by placing acid in a heat and pressure chamber, reproducing the natural conditions. The diamond crystalizes within six to ten weeks, after which it is polished and graded.

Lab-grown diamonds are often referred to as “synthetic,” but this doesn’t imply they are fake. They are identical to mined diamonds, having the same composition and properties. Therefore, lab-grown diamonds will pass any test for real diamonds, as they are genuine diamonds. Learn more about how lab diamonds are created.

Diamond Chemical Structure and Strength

Diamonds are composed of pure carbon, denoted by the chemical formula C. However, carbon also forms graphite and soot. The difference lies in the chemical structure specific to diamonds.

Carbon atoms can exist in various forms known as allotropes. In diamonds, every carbon atom is covalently bonded to another, forming a robust three-dimensional network. This allotrope is far stronger than those in graphite and soot.

How strong are diamonds compared to other minerals? As the densest form of pure carbon in nature, diamonds are the hardest known natural material. They are at the top of the Mohs hardness scale, which measures a mineral’s ability to visibly scratch another.