[meteorite-list] Earth's Most Abundant, But Hidden Mineral Finally Seen, Named (Bridgmanite)

[Ron Baalke]

http://www.livescience.com/46337-elusive-mineral-named-bridgmanite.html

Earth's Most Abundant, But Hidden Mineral Finally Seen, Named
By Jeanna Bryner
Live Science
June 16, 2014

[Image]
The elusive mineral bridgmanite is shown in a shock melt vein inside a 
4.5-billion-year-old meteorite found in Queensland, Australia.
Credit: Chi Ma

Earth's most abundant mineral lies deep in the planet's interior, sealed 
off from human eyes. Now, scientists for the first time have gotten a 
glimpse of the material in nature, enclosed inside a 4.5-billion-year-old 
meteorite. The result: They have characterized and named the elusive mineral.

The new official name, bridgmanite, was approved for the mineral formerly 
known by its chemical components and crystal structure - silicate-perovskite. 
The magnesium-silicate mineral was named after Percy Bridgman, a 1946 
Nobel Prize-winning physicist, according to the American Geophysical Union 
blog.

"It is a very exciting discovery," Chi Ma of Caltech and Oliver Tschauner, 
of the University of Nevada, Las Vegas, told Live Science in an email. 
"We finally tracked down natural silicate-perovskite (now bridgmanite) 
in a meteorite after a five-year investigation, and got to name the most 
abundant mineral on Earth. How cool is that?" 

The mineral likely resides beneath Earth's surface in an area called the 
lower mantle, between the transition zone in the mantle and the core-mantle 
boundary, or between the depths of416 and 1,802 miles (670 and 2,900 kilometers), 
scientists said.

Scientists have been searching for the mineral for a long time, because 
in order to identify a mineral one must know its chemical composition 
and crystal structure, Ma said.

Researchers found the bridgmanite in a meteorite that had fallen to Earth 
near the Tenham station in western Queensland, Australia, in 1879. The 
meteorite, Ma said, is highly shocked, meaning  it endured high temperatures 
and pressures as it slammed into other rocks in space. Those impacts can 
create shock veins of minerals within the meteorites. 

"Scientists have identified high-pressure minerals in its shock-melt veins 
since 1960s. Now we have identified bridgmanite," Tschauner said, referring 
to the Tenham meteorite. The meteorite is considered a chondrite, the 
most common type of meteorite found on Earth; scientists think these meteorites 
are remnants shed from the original building blocks of planets.

Most meteors (which are called meteorites once they strike Earth) are 
fragments of asteroids, while others are the cosmic dust discarded by 
comets. Rarely, meteorites represent impact debris from the moon and from 
Mars.

Ma and Tschauner used various methods to characterize the extracted mineral, 
including so-called synchrotron X-ray diffraction mapping and high-resolution 
scanning electron microscopy.

After five years of work, including multiple experiments, Ma and Tschauner 
sent their data for review to the International Mineralogical Association's 
Commission on New Minerals, Nomenclature and Classification (CNMNC), according 
to the AGU blog. The commission approved the mineral and new name on June 
2.