The Pentagon
The Pentagon was one one of the buildings to make use of Oolitic limestone Ken Hammond/Courtesty of the U.S. Air Force/Getty Images

Oolitic limestone, a popular building material that is found in iconic structures like the Buckingham Palace, the Pentagon, and Empire State building are the mineralised remains of prehistoric microbes that lived up to 200 million years ago during the Jurassic period, a new study has found.

Previously, oolitic limestone was thought to have been formed as a result of ooid grains rolling on the sea floor, slowly staking up the layers of sediment, but this snowball theory has now been debunked by a study done by the Australian National University (ANU).

The oolitic limestone is made up, almost entirely of millimetre-sized spheres stacked up on top of each other, leading to the now debunked assumption about its formation, notes the release. "We have proposed a radically different explanation for the origin of ooids that explains their definitive features," said Dr Bob Burne from the ANU Research School of Earth Sciences. "Our research has highlighted yet another vital role that microbes play on Earth and in our lives," he added.

Oolitic limestones from all geological periods have been found and identified, notes the report by ANU. There are such deposits spread out across the world including regions like the UK, Bahamas, China, the US, Germany, and Australia, to name a few.

Rogenstein Oolite from Germany made up entirely of millimetre-sized spheres Lannon Harley for ANU

"Many oolitic limestones form excellent building stones because they are strong and lightweight," Burne said. "Jurassic oolite in England has been used to construct much of the City of Bath, the British Museum and St Paul's Cathedral. Mississippian oolite found in Indiana in the US has been used to build parts of the Pentagon in Virginia and parts of the Empire State Building in New York City," he added.

"Our mathematical model explains the concentric accumulation of layers, and predicts a limiting size of ooids," said Professor Murray Batchelor from the Research School of Physics and Engineering and the Mathematical Sciences Institute at ANU. He led an international team of researchers and published their findings in the journal Scientific Reports.

The mathematical model used, notes Batchelor, was a tweaked version developed in 1972 to calculate the growth of brain tumours. He added that this study could be a way to understand how the climate has changed and how these past changes have affected the environment in prehistoric times.