In a report, published in the magazine Nature, a group of scientists say that X-ray and spectroscopic analysis of a small diamond found in magma from a Brazilian volcano showed a 40 micrometer speck of a mineral called ringwoodite. Further analysis revealed that its crystal lattice contains at least 1.4 percent water.
Ringwoodite is a variant of the mineral olivine, which makes up much of the earth’s mantle. Olivine does not absorb water. Below 400 kilometers, however, the immense heat and pressure changes its crystal structure, and the resulting substances can contain as much as 2.5 percent water.
Scientists say there is a fair chance that the place where the diamond was formed contains a lot of water whose highly pressurized steam could cause volcanic eruptions.