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Why we should stop ignoring the life stories of minerals

The crystals shouldn’t just be classified by shape alone, one scientist argues

Rocks may be made from a single mineral or many. But knowing the recipe of the molecules that make up a mineral tells only part of its story. One scientist wants to broaden their biographies.


WASHINGTON, D.C. — Every rock has a story. Understanding how it formed can tell scientists about the environment that surrounded the rock at its birth. But when scientists classify the minerals that make up rocks, they leave out the details of how those minerals formed. One scientist wants to change that. He wants to give minerals back their biographies. Knowing that history, he says, could help scientists understand more about our planet — and many others.

Minerals are solid substances that occur in nature. Up close, their molecules form regular, three-dimensional crystal patterns. A diamond is one example. Diamonds most often occur as cubic crystals. This means their atoms are stacked in repeating cube shapes. The whole rock (which can be made of one or more minerals) may end up with sharp edges too. It might be a cube, or it could be an octahedron, a shape with eight flat faces. Diamonds are a good example of how minerals with the same name can have different histories, says Andrew Christy. He’s is the curator of minerology at Queensland Museum in Brisbane, Australia. The big diamonds found in jewelry formed more than 160 kilometers (100 miles) below Earth’s surface, in the mantle. Heat and pressure there smushed carbon atoms together into cubes. That created diamond crystals. The ones we dig up today have been pushed to the surface through violent volcanic eruptions.

But diamonds can form elsewhere in the universe, as well. Tiny diamonds, for instance, form in meteorites crashing to Earth from space. Some of those meteorites have carbon atoms in them, Christy explains. When a meteorite blasts through Earth’s atmosphere, it can generate shockwaves of heat and pressure. “Those shockwaves passing through that carbon [in the meteorite] will create tiny, tiny diamonds,” Christy explains. Both of these rocks are diamonds. Based on their crystal structure, mineralogists would classify them the same. But Robert Hazen says scientists lose a lot when they take away the story of a mineral’s birth. “Natural minerals are storehouses of information,” he says. “They’re time capsules with vast amounts of information we have not yet explored.” Hazen is a mineralogist at the Carnegie Institution’s Geophysical Laboratory in Washington, D.C.

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