Davemaoite is a high-pressure calcium

silicate perovskite Silicate perovskite is either (the magnesium end-member is called bridgmanite) or (calcium silicate known as davemaoite) when arranged in a perovskite structure. Silicate perovskites are not stable at Earth's surface, and mainly exist in the l ...

(CaSiO₃) mineral with a distinctive cubic crystal structure. It is named after geophysicist Ho-kwang (Dave) Mao, who pioneered in many discoveries in high-pressure geochemistry and geophysics. It is one of three main minerals in Earth's lower mantle, making up around 5–7% of the material there. Significantly, davemaoite can host

uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...

and

thorium Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and ha ...

radioactive isotopes A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

which produce heat through radioactive decay and contribute greatly to heating within this region giving the material a major role in how heat flows deep below the Earth's surface. Davemaoite has been artificially synthesized in the laboratory, but was thought to be too extreme to exist in the Earth's crust. Then in 2021, the mineral was discovered as specks within a diamond that formed between 660 and 900 km beneath the Earth's surface, within the mantle. The diamond had been extracted from the

Orapa diamond mine The Orapa diamond mine is the world's largest diamond mining, mine by area. The mine is located in Orapa, a town in the Central District of Botswana about west of the city of Francistown. Orapa ("resting place for lions") is owned by Debswana, ...

Botswana Botswana, officially the Republic of Botswana, is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory part of the Kalahari Desert. It is bordered by South Africa to the sou ...

. The discovery was made by focusing a high-energy beam of

X-rays An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

on precise spots within the diamond using a technique known as

synchrotron A synchrotron is a particular type of cyclic particle accelerator, descended from the cyclotron, in which the accelerating particle beam travels around a fixed closed-loop path. The strength of the magnetic field which bends the particle beam i ...

X-ray diffraction X-ray diffraction is a generic term for phenomena associated with changes in the direction of X-ray beams due to interactions with the electrons around atoms. It occurs due to elastic scattering, when there is no change in the energy of the waves. ...

. Subsequently, a reappraisal of the data from the Orapa diamond and its inclusion cast doubt on the attribution to calcium silicate perovskite. Instead, the data were reinterpreted in terms of a diamond from the shallow part of the mantle with inclusions of minerals commonly found in microinclusions. Calcium silicate is found in other forms, such as

wollastonite Wollastonite is a calcium Silicate minerals, inosilicate mineral (calcium, Casilicon, Sioxygen, O3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or D ...

in the crust and breyite in the middle and lower regions of the mantle. However, davemaoite can exist only at very high pressure of around 200,000 times that found at Earth's surface.

References

Perovskites Calcium minerals {{mineral-stub

See also

References