On the subject of diamonds today:
What scientists found trapped in a diamond: a type of ice not known on Earth - LA Times March 9 2018
"Trapped in the rigid structure of diamonds formed deep in the Earth's crust, scientists have discovered a form of water ice that was not previously known to occur naturally on our planet.
The finding, published Thursday in Science
, represents the first detection of naturally occurring ice-VII ever found on Earth. And as sometimes happens in the scientific process, it was discovered entirely by accident."
and the original article in Nature:
CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle
Nature volume 555, pages 237–241 (08 March 2018)
"Laboratory experiments and seismology data have created a clear theoretical picture of the most abundant minerals that comprise the deeper parts of the Earth’s mantle. Discoveries of some of these minerals in ‘super-deep’ diamonds—formed between two hundred and about one thousand kilometres into the lower mantle—have confirmed part of this picture.."