“Each of these kinds of pyrite tells us something different about our planet, its origins, 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 a combination of the mineral’s species with its mechanism of origin (think volcanic pyrite versus microbial pyrite). Using machine learning analysis, they sifted through data from thousands of scientific papers and identified 10,556 different minerals.
Morrison and Hazen also identified 57 processes that individually or in combination created all known minerals. These processes included various forms of weathering, chemical precipitation, metamorphic transformation within the mantle, lightning strikes, radiation, oxidation, massive impacts during Earth’s formation, and even condensations in interstellar space before the planet was formed. They confirmed that the single largest factor in mineral diversity on Earth is water, which through a series of chemical and physical processes helps generate more than 80 percent of minerals.
But they also found that life is a key player: a third of all minerals are formed solely as parts or by-products of living things – such as bones, teeth, corals and kidney stones (all of which are rich in mineral content), or faeces, wood, microbial mats and other organic materials that over geologic time can absorb elements from their surroundings and transform into something resembling rock. Thousands of minerals are shaped by the activity of life in other ways, such as germanium compounds formed in industrial coal fires. Including substances created through interactions with the byproducts of life, such as the oxygen produced in photosynthesis, the fingerprint of life is on about half of all minerals.
Historically, scientists have “artificially 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 more fluid. Human bodies, for example, are made up of about 2% minerals by weight, most of it locked up in the calcium phosphate scaffolds that reinforce our teeth and bones.
How deeply the mineralogical is intertwined with the biological may not come as a huge surprise to earth scientists, Sahai said, but Morrison and Hazen’s new taxonomy “put a nice systematization on it and made it more accessible to a wider community.”
The new mineral taxonomy will be welcomed by some scientists. (“The old man sucked,” said Sarah Carmichaela mineralogy researcher at Appalachian State University.) Others such as Carlos Gray Santana, a philosopher of science at the University of Utah, stands by the IMA system, although it does not take into account the nature of mineral evolution. “It’s not a problem,” he said, because the IMA taxonomy was developed for applied purposes, such as chemistry, mining and engineering, and it still works beautifully in those fields. “It is good at meeting our practical needs.”