Maybe we were mistaken about Earth's mantle, the layer of our rocky planet that lies between its core and the thin crust on which we live.

For years, earth scientists were convinced that the mantle's entire lower region--which stretches from 400 to 1,800 miles below the surface--was composed of a particular structure of a mineral known as ferromagnesian silicate perovskite.

But now a new study conducted at Argonne National Laboratory in Illinois suggests that the extreme pressure and temperature (more than 3,500 degrees Fahrenheit) that exist about 1,200 miles below the surface cause the mineral to break into two distinct phases.

One layer is nearly devoid of iron, according to a written statement released by the lab. The other, called the H-phase, is full of the stuff.

"We still don't fully understand the chemistry of the H-phase," the study's lead author Dr. Li Zhang, a geophysicist at the Carnegie Institution of Washington, said in the statement. "But this finding indicates that all geodynamic models need to be reconsidered to take the H-phase into account. And there could be even more unidentified phases down there in the lower mantle as well, waiting to be identified."

For the study, scientists shone powerful beams of X-rays at a sample of ferromagnesian silicate held under extreme conditions similar to those found deep underground, causing it to break up and scatter in all directions. By analyzing data from the scatter, the scientists were able to reconstruct how the atoms in the sample were arranged.

There's no direct link between the new finding and the evolving science of earthquake prediction, Zhang told The Huffington Post in an email. But according to Dr. Yue Meng, another Carnegie geophysicist involved in the study, the finding "may significantly alter the prevailing theory of the lower mantle."