A landmark body of work led by the Carnegie Institution for Science details the origins and diversity of every known mineral on Earth, a landmark body of work that will help reconstruct the history of life on Earth, guide the search for new minerals and ore deposits, predict possible future life characteristics, and aid the search for habitable planets and extraterrestrial life.
Carnegie scientists Robert Hazen and Shaunna Morrison detail a novel approach to clustering (lumping) kindred species of minerals together or splitting off new species based on when and how they originated in twin papers published today by American Mineralogist and sponsored in part by NASA.
When mineral genesis is taken into account, the number of "mineral kinds" – a newly coined term – exceeds 10,500, roughly 75 percent more than the 6,000 mineral species recognized by the International Mineralogical Association (IMA) solely on the basis of crystal structure and chemical composition.
"This work fundamentally changes our view of the diversity of minerals on the planet," says Dr. Hazen of the Earth and Planets Laboratory at the Carnegie Institution for Science in Washington, DC.
Water mediated the transport of 80% of the Earth's minerals.
"Water, for example, mediated more than 80% of Earth's minerals, making it fundamentally important to mineral diversity on this planet. As a result, this explains why the Moon, Mercury, and even Mars have far fewer mineral species than Earth."
"The work also tells us something very profound about biology's role," he adds. "One-third of Earth's minerals could not have formed without biology, such as shells, bones, and teeth, or microbes, or the vital indirect role of biology, such as creating an oxygen-rich atmosphere, which resulted in the formation of 2,000 minerals that would not have formed otherwise."
"Each mineral specimen has a story to tell. Each one tells a different story. Each is a time capsule that reveals Earth's history in a way that nothing else can."
More than 40% of the Earth's mineral species formed in more than one way.
According to the paper, nature created 40% of Earth's mineral species in more than one way, such as abiotically and with the help of cells, and in some cases used more than 15 different recipes to produce the same crystal structure and chemical composition.
Nine of the 5,659 recognized mineral species studied by Hazen and colleagues arose from 15 or more different physical, chemical, and/or biological processes, ranging from near-instantaneous formation by lightning or meteor strikes to changes caused by water-rock interactions or transformations at high pressures and temperatures over hundreds of millions of years.
And, as if to demonstrate her sense of humour, Nature has created pyrite (aka Fool's Gold) in 21 different ways over the last 4.5 billion years, making it the mineral world's champion of diverse origins. Pyrite forms at high and low temperatures, with and without water, with and without the assistance of microbes, and in harsh environments where life has no place.
Pyrite is derived and delivered via meteorites, volcanoes, hydrothermal deposits, pressure between layers of rock, near-surface rock weathering, microbially-precipitated deposits, several mining-related processes including coal mine fires, and many other means.
To reach their conclusions, Hazen and Morrison created a database of every known mineral formation process. They identified 10,556 different combinations of minerals and modes of formation using large, open-access mineral databases (mindat.org and rruff.ima/info), which were supplemented by thousands of primary research articles on the geology of mineral localities around the world, as detailed in the paper "On the paragenetic modes of minerals: A mineral evolution perspective."
According to that paper and a sister paper published concurrently by the same journal, "Lumping and splitting: toward a classification of mineral natural kinds," co-authored by Drs. Hazen and Morrison in collaboration with mineralogists Sergey Krivovichev of the Russian Academy of Sciences and Robert Downs of the University of Arizona.
Their goal is to "understand how mineral diversity and distribution have changed over deep time and to propose a system of mineral classification that reflects mineral origins in the context of evolving terrestrial worlds."
Differentiating minerals based on how and when they appeared over Earth's 4.5 billion year history
Thousands of mineralogists around the world have meticulously documented nearly 6,000 different "mineral species" based on their unique combinations of chemical composition and crystal structure in previous studies spanning more than a century. Dr. Hazen and colleagues took a different approach, emphasizing how and when each type of mineral appeared over the course of more than 4.5 billion years.
"No one has ever attempted such a monumental task," says Dr. Hazen, who was awarded the IMA's 2021 medal for his outstanding achievements in mineral crystal chemistry, particularly in the field of mineral evolution.
"We are putting forth our best effort in these twin papers to lay the groundwork for a new approach to recognizing different types of minerals. We welcome the mineralogical community's insights, additions, and future versions."
New insights and conclusions from the papers include:
Water has played a dominant role in Earth's mineral diversity, forming more than 80 percent of mineral species.
Life played a direct or indirect role in the formation of nearly half of all known mineral species, with over 1,900 species formed entirely as a result of biological activities.
Rare elements play a disproportionate role in the mineral diversity of the Earth. Only 41 elements (less than 5 parts per million of Earth's crust) are essential constituents in over 2,400 (42 percent) of Earth's minerals. Arsenic, cadmium, gold, mercury, silver, titanium, tin, uranium, and tungsten are among the 41 elements.
Much of Earth's mineral diversity was established within the first 250 million years of its existence.
Some 296 known minerals are thought to predate Earth itself, with 97 of them only known from meteorites (with the age of some individual mineral grains estimated at 7 billion years — billions of years before the origin of our solar system)
The oldest known minerals are tiny, long-lasting zircon crystals that are nearly 4.4 billion years old.
Human activities have resulted in the formation of over 600 minerals, including over 500 minerals caused by mining, 234 of which were formed by coal mine fires.
According to the study, 3,349 (59%) of IMA-approved mineral species are known to occur from a single process (paragenetic mode), 1,372 (24%) from two processes, 458 (8%) from three processes, and the remaining 480 (8%) from four or more processes.
Diamonds, for example, are composed of carbon and have formed in at least nine ways, including condensation in the cooling atmospheres of old stars, during a meteorite impact, and deep within the Earth under hot ultra-high pressure.
These processes resulted in distinct diamond variants, such as stellar, impact, mantle, and ultra-high-pressure, which the authors refer to as "natural kinds."
The authors propose that, in addition to the IMA-approved mineral list, new categorizations and groupings be created based on the genesis of a mineral (paragenetic mode).
For example, 400 minerals formed by condensation at volcanic fumaroles – openings in the Earth's surface that emit steam and volcanic gasses – can be classified by science.
Other factors in mineral clustering and classification are discussed in the papers, such as the eon in which they formed. For example, Earth's "Great Oxidation Event" about 2.3 billion years ago resulted in the formation of new minerals at the planet's near-surface.
When water first appeared 4.45 billion years ago, the earliest water-rock interactions may have produced as many as 350 minerals in near-surface marine and terrestrial environments.
It also appears that hundreds of different minerals formed on Earth prior to the massive impact that vaporized much of our planet's crust and mantle and resulted in the formation of the Moon about 4.5 billion years ago. If this is the case, those minerals were obliterated, only to reappear as the Earth cooled and solidified.
The authors explain that "the sharp contrast between Earth's large complement of minerals and the relative mineralogical parsimony of the Moon and Mercury, as well as the modest diversity found on Mars, stems from differing water influences."
Aside from unintentional mineral formations in mining fires, humanity has created tens of thousands of mineral-like compounds that do not qualify for IMA recognition, such as building materials, semiconductors, laser crystals, specialty alloys, synthetic gemstones, plastic debris, and so on. All, however, are "likely to persist in the geologic record for millions of years, providing a clear sedimentary horizon that marks the so-called 'Anthropocene Epoch."
According to the paper, there are 77 "biominerals" formed by a variety of metabolic processes, ranging from corals, shells, and stinging nettles to minerals in bones, teeth, and kidney stones.
Another 72 minerals are derived directly or indirectly from bird and bat guano and urine. Spheniscidite is a rare mineral formed when penguin urine (order Sphenisciformes, hence the mineral name) reacts with clay minerals beneath a rookery on Elephant Island in the British Antarctic Territory.