The most abundant minerals we encounter daily, like quartz and feldspar, make up much of the Earth’s surface, but they represent a tiny fraction of the planet’s total mass. The true composition of Earth is dominated by substances hidden beneath the crust, where extreme pressure and temperature conditions forge different materials entirely. Understanding what mineral is most abundant requires looking past the familiar surface and considering the vast, unseen layers that constitute the bulk of our world. The answer is surprisingly counterintuitive, as the most common mineral on our planet remained unnamed and unstudied in its natural form until recently.
Defining Earth’s Mineral Abundance
To determine the most abundant mineral, it is necessary to first define what a mineral is—a naturally occurring, inorganic solid with a specific chemical composition and an orderly, repeating atomic structure called a crystal structure. The crystal structure is what gives a mineral its unique physical properties, and it is highly dependent on the conditions under which the mineral forms. The primary distinction for mineral abundance lies between the Earth’s thin crust and the entire planet.
The crust, where humans live and explore, is composed primarily of silicate minerals like feldspar (40% to 60%) and quartz (about 12%). However, the crust represents only about one percent of Earth’s total volume. The planet’s mass is overwhelmingly contained in the mantle and the core. Therefore, the mineral that dominates the entire Earth must be the one that is stable under the crushing pressures of the deep interior.
Bridgmanite: The Planet’s Most Plentiful Mineral
The most abundant mineral on Earth is Bridgmanite, a high-pressure, high-density magnesium-iron silicate perovskite. This mineral was long theorized by scientists but remained a mineralogical mystery because it cannot survive the transition to the Earth’s surface. Its ideal chemical formula is \((\text{Mg},\text{Fe})\text{SiO}_3\), meaning it is primarily composed of magnesium, iron, silicon, and oxygen.
Bridgmanite possesses a highly dense perovskite crystal structure, which is a specific arrangement of atoms where magnesium and iron ions occupy the larger sites, and silicon ions occupy the smaller, six-sided sites. Because the International Mineralogical Association requires a natural sample for a mineral to be officially named, it was only in 2014 that Bridgmanite received its official name. Researchers were finally able to isolate and characterize a naturally occurring sample from the highly shocked Tenham meteorite that fell in Australia in 1879.
This discovery solidified its status, naming it after the Nobel Prize-winning physicist Percy Bridgman, who pioneered high-pressure physics experiments. Before 2014, scientists referred to it by its chemical and structural description, silicate perovskite. The natural Bridgmanite found within the meteorite’s shock veins formed under pressures and temperatures comparable to those deep within the planet, preserving its structure for study.
The Deep Earth Conditions That Create Bridgmanite
Bridgmanite is the dominant material of the Earth’s lower mantle, the layer extending from roughly 660 kilometers down to the core-mantle boundary at about 2,900 kilometers. This single mineral constitutes approximately 38% of the Earth’s entire volume. It is stable only under the extreme physical environment of this deep layer, where pressures range from about 24 gigapascals to over 120 gigapascals and temperatures reach thousands of degrees Celsius.
The immense pressure forces the atoms of magnesium, iron, silicon, and oxygen into the compact perovskite structure, which is significantly denser than the minerals found in the upper mantle. This dense packing is why Bridgmanite is volumetrically significant and plays a major role in the planet’s dynamics. The physical properties of Bridgmanite influence the speed of seismic waves and are integral to understanding heat transfer and mantle convection, the slow churning motion that drives plate tectonics.
Because Bridgmanite is a high-pressure phase, it is thermodynamically unstable at the low pressures found at the Earth’s surface. If it were brought up from the lower mantle, it would instantly transform into a less dense assemblage of other minerals, which is why it was never found in terrestrial rocks. The meteorite sample survived because the pressure drop during the impact event was extremely rapid, essentially freezing the Bridgmanite crystals in place before they could break down.