What is the most common mineral on Earth?

Picture the most common mineral on Earth. You are probably imagining something you have actually seen: sand on a beach, the sparkle in a granite benchtop, a rock in your garden. Fair enough. But the true champion is a mineral that no human had ever held a natural sample of until 2014, and the first one turned up in a space rock in outback Australia.

The short answer

Earth’s most abundant mineral is bridgmanite, a dense silicate with the formula (Mg,Fe)SiO3. It is thought to dominate the lower mantle, the vast layer roughly 670 to 2,900 kilometres beneath our feet, where heat and pressure are crushing. Scientists had studied it for decades in the lab under the clunky name silicate perovskite, but a mineral cannot get an official name until a natural sample is found and fully described.

The real story

That was the problem. You cannot drill to the lower mantle, and bridgmanite stays sealed away deep inside the planet, far beyond human reach. So where do you find a rock formed under extreme pressure? In something that has been smashed very hard.

Enter the Tenham meteorite, which fell in 1879 near Tenham station in western Queensland, Australia. It is about 4.5 billion years old, and violent collisions in space had subjected parts of it to shock conditions similar to those deep inside Earth. Another high-pressure mineral, ringwoodite, had already been found in the same meteorite back in the 1960s.

In 2009 two mineralogists, Chi Ma of Caltech and Oliver Tschauner of the University of Nevada, Las Vegas, began hunting through thin shock-melt veins in Tenham for the elusive mineral. It was a fiddly job: the crystals were tiny, and electron beams used to examine them tended to damage them. The team eventually used synchrotron X-ray diffraction to pin down the crystal structure. After about five years of work they submitted it to the International Mineralogical Association in March 2014, and the name was approved on 2 June 2014.

The name honours Percy Bridgman, the physicist who won the 1946 Nobel Prize in Physics for his work on high-pressure physics. Fitting, really: a mineral that only exists under enormous pressure, named after the man who made a career out of squeezing things.

So the most plentiful mineral on our planet was officially christened less than a generation ago, and its first confirmed natural specimen came not from Earth’s interior but from a chunk of the early solar system that landed on a cattle station.

Why people get it wrong

We judge what is common by what we see, and we only ever see a thin skin of the planet. Surface minerals like quartz feel ubiquitous because they are in our sand, our soil and our kitchen benches, but they are the frosting, not the cake. The bulk of the cake is bridgmanite, sitting hundreds of kilometres down where nobody has ever been.

The Sole puts it plainly: “The most common mineral on Earth was found in Queensland, inside a rock that fell from space. Typical. You wait billions of years and it turns up on a cattle station.”