The latest discovery of how diamonds reach the surface reveals that ultrafast and explosive volcanic eruptions are responsible for carrying precious stones from the depths of the Earth’s mantle, to the layer between the Earth’s crust and core.
Researchers at the University of Oslo published, in September 2025, a study in the journal Geology detailing the chemical mechanism behind this rare process.
Scientist Ana Anzulović and her team used advanced models to understand kimberlite magma, a volcanic material capable of traveling at speeds of up to 130 km/hstarting from depths greater than 150 kilometers.
The study clarifies how stones resist the journey without transforming into graphite – the stable form of carbon at low pressures. Scientific discovery brings new perspectives to geology and understanding the planet’s dynamics.
How and where do diamonds form inside the Earth?
The origin of diamonds occurs in deep regions of the Earth’s mantle, under extreme pressures and temperatures. Under these conditions, more than 150 kilometers from the crust, carbon atoms crystallize to form the gem. However, the crystal only survives the trip if transportation is carried out quickly.
The mechanism by which diamonds reach the surface depends on kimberlites, which are volcanic tubes. They function as natural magma elevators.
Rare volcanoes capture precious stones in the mantle and propel them upward before heat turns them into graphite, the common carbon used in pencils.
During the ascent, the magma tears off pieces of rock called xenoliths, fragments coming from great depths. He also carries xenocrystals, which are individual crystals, like diamond.
These elements serve as a chemical record of the path taken, helping scientists to map the planet’s interior precisely.
What “explosive” mechanism allows magma to rise?
The rise of kimberlitic magma occurs due to the buoyancy of the material in relation to neighboring rocks. By simulating mantle pressures, scientists at the University of Oslo discovered that magma needs to be less dense to rise. The chemical model tested different mixtures to understand how the material passes through the crust without interrupting its flow.
Ana Anzulović, lead researcher of the study, explains that the process works like collecting samples of the kimberlite at different pressure points. The models showed that magma can carry up to 44% of peridotite, a type of dense rock from the Earth’s mantle.
The heavy load is able to reach the top because the fluid remains in accelerated motion throughout the journey. The speed of 130 km/h is driven by the low viscosity (resistance to flow) of the enriched magma.
Therefore, this “explosive” mechanism allows diamonds to cross the Moho, which is the seismic transition line between the mantle and the crust. Without this speed, the crystals would undergo chemical changes before reaching the surface.
Why are rashes so rare?
The process of how diamonds reach the surface is a rare volcanism that depends on volatile compounds, elements that turn into gas quickly. The 2025 study reveals that without carbon dioxide, magma becomes dense and remains trapped in the mantle.
Chemical balance explains why volcanic vents are scarce and located in very old continental areas.
The rarity also arises from the movement of land masses. According to Dr. Tom Gernon, from University of Southamptoneruptions follow the rhythm of formation and breakup of supercontinents.
The 2023 study carried out by Gernon in collaboration with researchers from universities in Europe, North America and Australia, points out that the phenomenon occurred around 30 million years after continental separation.
Recent geological research points to the role of CO2 and water
Mantle chemistry reveals that carbon dioxide and water serve as the components that explain how diamonds reach the surface.
Water acts by increasing diffusivity, that is, the ease with which molecules move in the fluid, which keeps the magma mobile. The state of fluidity allows volcanic material to slide through cracks in the rocks.
Carbon dioxide exerts a structural function under high pressure, but changes its behavior when approaching the Earth’s crust. Near the surface, the gas separates from the liquid in a process called degassing. This generates the pressure needed to propel the eruption upward with explosive force.
Researcher Ana Anzulović demonstrated that the Jericho kimberlite, in Canada, requires at least 8.2% carbon to erupt.
“I was really surprised to find that I can take such a small system and actually observe, ‘Okay, if I don’t add carbon, this magma will be denser than the craton, so it won’t erupt,’” Anzulović said in a statement. “It’s great that modeling the chemistry of kimberlite can have implications for such a large-scale process.”, he adds.
New perspectives for diamond exploration and geological studies
Recent geological research offers tools to optimize mining by generating knowledge that indicates where to look for diamond deposits on ancient continentsstill hidden in deep pipes. The exploration strategy becomes more accurate with this data.
Understanding the processes of the Earth’s mantle is also necessary for geodynamics. The study links tiny atomic movements to continental-scale events.
The next steps in science will test whether other volcanoes follow the pattern seen in Canada, according to Gernon. Technological advances can help decipher the other mysteries that are hidden inside planet Earth.
