![Backscattered electron images of experimental charges. Locations of images (A) to (D) from sediment-peridotite reaction experiments are schematically shown in capsule on the left. (A, C, and D) - reaction experiments at 5 GPa/1000 degrees Celsius with superimposed energy-dispersive x-ray maps of chlorine [green in (C) and (D)]. The sediment half of two-layer experiments recrystallized to garnet and clinopyroxene (Cpx), whereas orthopyroxene (Opx), magnesite (Mgs), and Na-K chlorides formed at the leading edge of the reaction zone against the peridotite. (B) - peridotite layer in the reaction experiment at 3 GPa/900 degrees Celsius contained phlogopite (Phl) behind the magnesite plus orthopyroxene zone, and Na-K chlorides were absent. (E and F) - sediment melting experiment (no peridotite included) at 4 GPa/1000 degrees Celsius showing silicate melt (E) in equilibrium with garnet (Gt), coesite (Coe), and Mg calcite (Mg-Cc) shown in (F). Scale bars - 100 μm (A and B) and 20 μm (C to F). Image credit: Förster et al, doi: 10.1126/sciadv.aau2620.](https://cdn.sci.news/images/2019/05/image_7241-Diamond-Salts-370x215.jpg)
So-called fibrous diamonds, which are cloudy and less appealing to jewelers — and less often, gem-quality diamonds — trap and preserve fluids that are present during their formation. In a series of high-pressure, high-temperature experiments, an international team of geoscientists has demonstrated that seawater in sediments from the bottom of the ocean reacts in the right way to produce the balance of salts found in fibrous diamonds. Backscattered...
