As Life Evolves, Minerals Do Too: Team Recounts Dramatic Changes in Variety, Abundance
Perkins, Sid, Science News
If you think evolution is something that happens only to plants and animals, think again. Evolution--change through time--happens in the mineral kingdom as well, scientists say. As the solar system has aged, the number of types of minerals it contains has burgeoned from only a dozen or so to more than 4,000.
And about two-thirds of today's minerals either directly or indirectly evolved thanks to the presence of life on Earth.
"Four billion years ago, the world's minerals were radically different than they are today," says Robert Hazen, a geophysicist at the Carnegie Institution for Science in Washington, D.C. He and his colleagues chronicle the long-term growth in Earth's mineral complexity in the November-December American Mineralogist.
"This is the first change in the way that geologists look at minerals in more than two centuries," comments Carl Francis, curator of the Mineralogical Museum at Harvard University.
Billions of years ago, the solar system was nothing more than a cloud of gas and dust. Although that material contained all of the naturally occurring elements found in the periodic table, minerals are more than their specific chemical formulas. Minerals also have distinct crystalline structures. Most of the elements were too rare or widely dispersed to create minerals of their own, says Hazen.
In all, the tiny particles of interstellar dust that populated the nascent solar system--like those that still drift through space today--contained only a dozen or so minerals. These dust particles, primarily made of carbide, oxide, nitride and silicate minerals, were the raw materials of today's planets, the researchers note.
As the dust clumped into larger masses and the sun ignited, changing conditions spawned new minerals. In the billions-of-years-old, meteorite-sized masses that fall to Earth today--which presumably reflect the composition of masses that formed early on--scientists have identified about 60 minerals, says Hazen. About 20 of those are found only in crystals a few micrometers across or smaller. …