“Each of those types of pyrite tells us something different about our planet, its origin, about life and how it has changed over time,” Hazen said.
For that reason, the new papers classify minerals by “species,” a term Hazen and Morrison define as combining the mineral species with its mechanism of origin (think volcanic pyrite vs. microbial pyrite). Using machine learning analysis, they searched data from thousands of scientific papers and identified 10,556 different types of minerals.
Morrison and Hazen also identified 57 processes that individually or in combination created all known minerals. These processes include various types of weathering, chemical fallout, metamorphic transformation in the mantle, lightning strikes, radiation, oxidation, massive impacts during Earth’s formation, and even condensations in interstellar space before the planet formed. They confirmed that the greatest factor in Earth’s mineral diversity is water, which through a variety of chemical and physical processes helps generate more than 80 percent of the minerals.
Blue-green formations of malachite form in copper deposits near the surface as they weather. But they could not form until after life increased oxygen levels in the air, about 2.5 billion years ago.Photo: Rob Lavinsky/ARKENSTONE
But they also found that life is a major player: a third of all types of minerals are formed solely as parts or byproducts of living things, such as bits of bones, teeth, coral and kidney stones (all of which are rich in minerals), or feces, wood, microbial mats and other organic materials that can absorb elements from their environment over geological time and turn them into something more like stone. Thousands of minerals are formed in other ways by the activity of life, such as germanium compounds that form in industrial coal fires. Including substances created by interactions with by-products of life, such as the oxygen produced in photosynthesis, life’s fingerprints are on about half of all minerals.
Historically, scientists have “artifically drawn a line between what is geochemistry and what is biochemistry,” he said Nita Sahai, a biomineralization specialist at the University of Akron in Ohio who was not involved in the new research. In reality, the line between animal, vegetable and mineral is much smoother. Human bodies, for example, are made up of about 2 percent minerals, most of which is locked up in the calcium phosphate scaffold that strengthens our teeth and bones.
How deeply the mineralogical is intertwined with the biological may not be a big surprise to Earth scientists, Sahai said, but Morrison and Hazen’s new taxonomy “has done a nice systematization to it and made it more accessible to a wider community.”
Some scientists will applaud the new mineral taxonomy. (“The old one was bad,” said Sarah Carmichaela mineralogy researcher at Appalachian State University.) Others, such as: Carlos Gray Santana, a philosopher of science at the University of Utah, are behind the IMA system, even though it doesn’t take into account the nature of mineral evolution. “That’s not a problem,” he said, because the IMA taxonomy was developed for applied purposes, such as chemistry, mining and engineering, and it still functions beautifully in those areas. “It satisfies our practical needs well.”