Mineral physics
Many of the pioneering studies in mineral physics involved explosions or projectiles that subject a sample to a shock.
Pressures of about 28 GPa (equivalent to depths of 840 km),[3] and temperatures above 2300 °C,[4] can be attained using WC anvils and a lanthanum chromite furnace.
The apparatus is very bulky and cannot achieve pressures like those in the diamond anvil cell (below), but it can handle much larger samples that can be quenched and examined after the experiment.
[5] Recently, sintered diamond anvils have been developed for this type of press that can reach pressures of 90 GPa (2700 km depth).
It can compress a small (sub-millimeter sized) piece of material to extreme pressures, which can exceed 3,000,000 atmospheres (300 gigapascals).
The concentration of pressure at the tip of the diamonds is possible because of their hardness, while their transparency and high thermal conductivity allow a variety of probes can be used to examine the state of the sample.
Achieving temperatures found within the interior of the earth is just as important to the study of mineral physics as creating high pressures.
Laser heating is continuing to extend the temperature range that can be reached in diamond-anvil cell but suffers two significant drawbacks.
[citation needed] To deduce the properties of minerals in the deep Earth, it is necessary to know how their density varies with pressure and temperature.
A simple example of an EOS that is predicted by the Debye model for harmonic lattice vibrations is the Mie-Grünheisen equation of state: where
A very useful heuristic was discovered by Francis Birch: plotting data for a large number of rocks, he found a linear relation of the compressional wave velocity
[9]: 107–109 The field of mineral physics was not named until the 1960s, but its origins date back at least to the early 20th century and the recognition that the outer core is fluid because seismic work by Oldham and Gutenberg showed that it did not allow shear waves to propagate.
[16] A landmark in the history of mineral physics was the publication of Density of the Earth by Erskine Williamson, a mathematical physicist, and Leason Adams, an experimentalist.
Working at the Geophysical Laboratory in the Carnegie Institution of Washington, they considered a problem that had long puzzled scientists.
They concluded that the Earth's mantle had a different composition than the crust, perhaps ferromagnesian silicates, and the core was some combination of iron and nickel.
[17] In 1952, he published a classic paper, Elasticity and constitution of the Earth's interior, in which he established some basic facts: the mantle is predominantly silicates; there is a phase transition between the upper and lower mantle associated with a phase transition; and the inner and outer core are both iron alloys.
