Diamonds may be forever, but that's not true of most minerals. In fact, about two-thirds of the 4,300 known minerals on Earth today owe their existence to biological processes, and thus evolved fairly recently in geological terms. So says Robert M. Hazen of the Carnegie Institution in Washington, D.C., who with seven colleagues identified three phases of mineral evolution.
The first phase began more than 4.55 billion years ago, as the solar system started developing. Chemical elements came together, forming about 250 simple minerals that in turn coalesced into planets. On Earth, the second phase stretched from 4.55 billion to 2.5 billion years ago, starting with the violent collision that formed the Moon. Earth's temperature and pressure varied wildly; plate tectonics began churning the planet's surface; and volatiles appeared, such as water and carbon dioxide, helping to redistribute the elements. Those changes enabled the evolution of some 1,250 new minerals.
Finally, during the past 2.5 billion years, biological processes — particularly photosynthesis — have profoundly affected mineral composition by oxygenating the atmosphere and thus promoting oxidation of ores. Malachite, turquoise, and nearly 3,000 other minerals could occur only on a living planet, Hazen says.
Minerals do not undergo such Darwinian processes as natural selection or competition for niches. Still, Hazen notes, mineral evolution is more than simple change overtime. The diverse and complex mineral assemblages on Earth today result from a sequence of irreversible physical and biological processes, starting with those simple pre-solar accretions.
The reseach was detailed in the American Mineralogist.
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