Calcium silicate perovskite (CaSiO3), the interior earth mineral, is the most geochemically important phase in the lower mantle. It concentrates elements that are incompatible in the upper mantle, including the heat-generating elements thorium and uranium, which have half-lives longer than Earth’s geologic history.
The mineral showed up as infinitesimal small dark specks in a diamond unearthed from an African mine in the 1980s. Now, UNLV geochemists have discovered this mineral- entrapped in a diamond- on the surface of the Earth. This is the first time that lower mantle minerals have ever been observed in nature.
The mineral usually falls apart before reaching the Earth’s surface, unable to retain its structure outside of a high-pressure environment. In this case, the diamond’s incredible strength preserved the mineral.
According to scientists, this interior earth mineral traveled up to the surface from 410 miles deep within the Earth’s lower mantle.
The diamond, which the mineral found, arrived on the surface decades ago in Botswana via the Orapa mine, the world’s largest diamond mine by area. In 1987, a mineralogist at the California Institute of Technology in Pasadena bought this diamond.
Recently, geochemists at UNLV got their hands on the diamond. By using a new suite of scientific tools, they analyzed the interior structure of the diamond. They found a new crystalline compound that they named “davemaoite.”
It has been named ‘davemaoite’ after Ho-Kwang “Dave” Mao, an experimental geophysicist who developed many techniques that Tschauner and his colleagues use today.
UNLV mineralogist Oliver Tschauner, who led the study, said, “For jewelers and buyers, the size, color, and clarity of a diamond all matter, and inclusions — those black specks that annoy the jeweler — for us, they’re a gift. I think we were very surprised. We didn’t expect this.”
The Commission of New Minerals, Nomenclature, and Classification of the International Mineralogical Association approved this mineral as a new natural mineral.
Tschauner said, “Davemaoite originated between 410 and 560 miles below the Earth’s surface, and its discovery highlights just one of two ways that we find highly pressurized minerals in nature: from deep within Earth’s interior or inside meteorites.”
- Oliver Tschauner et al. Discovery of davemaoite, CaSiO3-perovskite, as a mineral from the lower mantle. DOI: 10.1126/science.abl8568