It sounds weird, but the most abundant mineral on Earth finally got a name last week, thanks to a century-old meteorite. What? How? Why did it take so long? There were a whole confluence of reasons it took bridgmanite so long to get its name.
The first thing you should know is that, aside from the photo at the top of this post, you've never seen bridgmanite. The mineral formerly referred to as a silicate perovskite only exists at the high temperatures and pressures of the Earth's lower mantle, where no human or drill dares to go. That's about 640km to 2900km below the Earth's surface. Although lab tests and models pointed toward its existence, geologists have never been able to see bridgmanite or characterise its structure.
Enter meteorites! Meteors that have collided with objects in space and then crashed into Earth will have survived some intense pressures and temperatures — not unlike what happens in the Earth's crust. Just like diamonds, which can either form in the Earth's mantle or because of a meteorite collision.
So a team of mineralogists decided to study the Tenham meteorite, which landed in Queensland, Australia in 1879. Specifically, they looked at the meteorite's "shock-induced melt veins", scars of past violent collisions. Using a technique called synchrotron X-ray diffraction, which shoots powerful X-rays at a sample, the team characterised the mineral's molecular makeup (MgSiO3) and structure.
But still, if we knew about it, why didn't it have a name? Turns out that the International Mineralogical Association, the gatekeeper for minerals, only allows minerals to be named when their structures are known. So here we finally have it: bridgmanite, named after physicist Percy Bridgman who won a Nobel prize for high pressure physics. We've waited long enough, but it seems like an appropriate name. [GeoSpace]
Picture: Chi Ma via AGU