Minerals Love Life
It was not until recently that scientists even thought about how the mineral kingdom may have changed over time. Traditionally classified by composition, structure, and other features, the age of a mineral was usually ignored. That changed in the mid 2000s when Bob Hazen wondered why only 12 minerals existed in our corner of the cosmos before the Solar System formed 4.6 billion years ago and now there are more than 4,500. That sparked his pioneering research into mineral evolution. Surprisingly, he found out that the emergence of early life kindled some two-thirds of today’s minerals. The work suggests that looking for specific minerals on other planets and moons could enhance the search for extraterrestrial life.
Hazen and colleagues have identified three eras of mineral evolution—early Solar System formation, when planets started to aggregate; the time when Earth’s crust and mantle began to change; and the time when the Earth’s surface interacted with biology. These three eras are further subdivided into 10 stages. But it was the Great Oxidation Event, about 2.4 to 2.1 billion years ago, that triggered an explosion of new minerals. That is when photosynthetic microorganisms began their rise, releasing oxygen, with the result that chemical reactions with oxygen and water at the near surface went wild.
The Big Bang produced just hydrogen, helium, and a smattering of lithium. Other elements formed over millions of years as giant stars processed materials in their cores. When they exploded as supernovae, the first dozen minerals (mostly diamond, graphite, silicates, and oxides) crystallized. More than 250 different minerals formed in the earliest Solar System as dust and gas accumulated into planetesimals. On Earth, volcanoes, plate tectonics, water-rock interactions, and other geological changes 4.5 to 2.5 billion years ago led to the first continents and some 1,500 new minerals. But the emergence of life almost tripled the mineral population to more than 4,000.
Currently, Hazen is looking at the first appearances of minerals containing specific elements. The research shows a notable increase in mineral diversity between 2.8 to 2.5, 2.0 to 1.8, and 0.43 to 0.25 billion years ago—when supercontinents were assembling and mountain building led to mineralization. Hazen recently found that many mercury-related minerals first occur in formations dating from about 400 million years ago when the element interacted with organic matter with the rise of the biosphere. These and other findings will be entered into a new Mineral Evolution Database under development, which no doubt will reveal other patterns.