A study on 10,000 kinds of Earth's minerals could help us discover extraterrestrial life

"Many previous scientists have studied the origins of minerals individually, but no one before has done a comprehensive survey of all minerals and all of the ways they form," said Hazen in an interview with IE. "Also, we view minerals for the first time from the lens of "mineral informatics." Each specimen is an information-rich time capsule, waiting to be opened."

Information-rich, minerals can offer an insight into the evolution of planetary bodies. Therefore, it is imperative to analyze and interpret this abundance of data to understand the origin and evolution of life.

Biology and its role in planet geology

Traditionally, crystalline compounds were classified based on the atoms they contained and how these were arranged. Large, expensive mass spectrometers and other devices were used to classify the structures, compositions, and properties of minerals.

While such earlier studies documented almost 6,000 different "mineral species" based on their unique combinations of chemical composition and crystal structure, Hazen and colleagues took a different approach, emphasizing how and when each kind of mineral appeared through more than 4.5 billion years of Earth history, giving them context.

The researchers wanted to learn more about the beginnings of planetary evolution. "We want to know how Earth and other planets evolved; we want to understand the co-evolution of life and rocks; we want to understand what makes Earth different from other planets and moons; we want to discover new mineral deposits and better characterize known deposits," he said. "All of those questions and more can be addressed by studying the evolving diversity and distributions of minerals through 4.5 billion years."

A lot of the takeaways from the study are intriguing. For example, the role minerals play in the global water cycle. "More than 80 percent of Earth's mineral diversity is a consequence of water and its interactions with rocks," said Hazen.

This explains one of the key reasons why the Moon, Mercury, and even Mars have far fewer mineral species than Earth.

The research also speaks volumes about the role of biology. "More than half of Earth's minerals can form as a consequence of life, with more than one-third only forming through biology. Not only is Earth's mineral diversity unique among known worlds, but we speculate that Earth's mineral diversity is, itself, a biosignature," said Hazen. 

One mineral; 21 different ways

The International Mineralogical Association (IMA) defines around 5,600 listed species - a list assembled over centuries. Hazen and Morrison have now increased the number to 10,500 of what they term "mineral kinds." This term states takes into account that many minerals can be formed in several different ways.

For example, there are nine different kinds of diamonds based on their form variations. These include those baked from the ultra-high pressure deep within the Earth, diamonds that were formed from a meteor strike, and more. But, no mineral in the catalog has as many different kinds as pyrite, also known as Fool's Gold. It has been created in 21 different ways over the past 4.5 billion years. The mineral forms at high temperatures and low, with and without water, with the help of microbes, and in harsh environments where life plays no role whatsoever.

Forty percent of the Earth's mineral species were created in more than one way - both abiotically and with a helping hand from biological life such as animals and microbes. 

While 80 percent of Earth's minerals were borne of water-rock interactions, nine percent were formed through only one process. Just eight percent of the minerals were formed through four or more processes. 

'A living document' that will be constantly updated

Of the 5,659 recognized mineral species surveyed by the researchers, nine can come into being via 15 or more different physical, chemical, and/or biological processes - everything from the near-instantaneous formation by lightning or meteor strikes to changes caused by water-rock interactions or transformations at high pressures and temperature spanning hundreds of millions of years.

Minerals formed through these different interactions could also provide hints of long-extinct life or the existence of an ancient ocean.

Now, how accurate is the data?

"This is a great question that we think about a lot," said Hazen. "Every report of a mineral and formation environment comes from the peer-reviewed literature. We identify more than 10,500 combinations of a mineral "species" and a formation process. We estimate that at least 90 percent of those reports are highly reliable, while the remaining 10 percent range from likely, to best guess, to uncertain. The database we developed is thus a "living document" that we and others will constantly expand and update. Despite any uncertainties, the studies' major conclusions are statistically robust," he explained.

The new mineral cataloging system democratizes mineral science by relying on known processes based on the vast published literature that has never been compiled into open-access data resources. The researchers have identified 10,556 different combinations of minerals and modes of formation, detailed in the paper, "On the paragenetic modes of minerals: A mineral evolution perspective," making it instantly accessible to anyone. 

A new way to teach mineralogy

As aforementioned, while the study helps understand how planets form and evolve, it also has implications beyond the research on the origin of life.

It can be used for "predicting and discovering the localities of new mineral resources; for choosing the best targets for future space missions; for understanding some of the complex feedbacks between the geosphere and biosphere; for outlining a new way to teach mineralogy, and to present mineral collections in natural history museums (many museums are reorganizing their collection displays according to this new system)," explained Hazen.

The researchers also noted that several of the most essential mineral-forming processes, such as the development of the oceans and the continental crust, would have occurred during Earth's first billion years or even earlier.

If life is "a cosmic imperative that emerges on any mineral- and the water-rich world," the authors said in a statement, "then these findings support the hypothesis that life on Earth ​emerged rapidly, in concert with a vibrant, diverse Mineral Kingdom, in the earliest stages of planetary evolution."

"In addition to chemical composition and physical properties, Hazen emphasizes their conditions and contexts of formation, and a new way of seeing minerals appears," said Patrick Cordier, a mineralogist at the University of Lille in France, in a statement. 

What's next?

"The first is the nitty-gritty work of completing the "Evolutionary System of Mineralogy," which is being published as separate lengthy peer-reviewed papers (7 down, 5 to go) before being collated into a book-length reference work. That's my main effort," said Hazen. "Meanwhile, Dr. Shaunna Morrison, who is the world's leader in mineral informatics, will be publishing a series of studies on the analysis and visualization of mineral data, as applied to mineral discovery, comparative planetology, Earth evolution, and more," he added.