The mineral diversity of Earth is unique and could not be duplicated anywhere in the cosmos. That’s according to a group of researchers, led by Dr Robert Hazen at the Carnegie Institution of Washington. The team also predicts that our planet has more than 1,500 undiscovered minerals.
According to Dr Hazen and co-authors, most of Earth’s 5,000 mineral species are rare, known from only a few localities. Image credit: NOAA / NASA / U.S. Air Force.
Minerals form from novel combinations of elements. These combinations can be facilitated by geological as well as biological activity, such as chemical reactions with oxygen and organic material.
In the 2000s, Dr Hazen proposed the idea that the diversity explosion of Earth’s minerals from the dozen present at the birth of our Solar System to the nearly 5,000 types existing today arose primarily from the rise of life.
According to Dr Hazen, more than 70 percent of known minerals can be linked directly or indirectly to biological activity. Much of this is due to the rise of bacterial photosynthesis, which dramatically increased the atmospheric oxygen concentration about 2.4 billion years ago.
In a suite of four papers, published in the journals Canadian Mineralogist; Mathematical Geoscience; American Mineralogist; and Earth and Planetary Science Letters, Dr Hazen and his colleagues took the mineral evolution concept one step further.
They used both statistical models of ecosystem research and extensive analysis of mineralogical databases to explore questions of probability involving mineral distribution.
They discovered that the probability that a mineral ‘species’ exists at only one locality is about 22 percent, whereas the probability that it is found at 10 or fewer locations is about 65 percent.
Most mineral species are quite rare, in fact, found in 5 or fewer localities.
“Minerals follow the same kind of frequency of distribution as words in a book,” Dr Hazen said.
“For example, the most-used words in a book are extremely common such as and, the, and a. Rare words define the diversity of a book’s vocabulary. The same is true for minerals on Earth. Rare minerals define our planet’s mineralogical diversity.”
Further statistical analysis of mineral distribution and diversity suggested thousands of plausible rare minerals either still await discovery or occurred at some point in Earth’s history.
Dr Hazen’s team predicted that 1,563 minerals exist on Earth today, but have yet to be discovered and described.
Further expanding the link between geological and biological evolution, the scientists applied the biological concepts of chance and necessity to mineral evolution.
In biology, this idea means that natural selection occurs because of a random ‘chance’ mutation in the genetic material of a living organism that becomes, if it confers reproductive advantage, a ‘necessary’ adaptation.
But in this instance, the researchers asked how the diversity and distribution of Earth’s minerals came into existence and the likelihood that it could be replicated elsewhere.
What they found is that if we could turn back the clock and re-play Earth’s history, it is probable that many of the minerals formed and discovered in this alternate version of our planet would be different from those we know today.
“This means that despite the physical, chemical, and biological factors that control most of our planet’s mineral diversity, Earth’s mineralogy is unique in the cosmos,” Dr Hazen concluded.
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Robert M. Hazen et al. Mineral ecology: chance and necessity in the mineral diversity of terrestrial planets. Canadian Mineralogist, published online July 24, 2015; doi: 10.3749/canmin.1400086
Grethe Hystad et al. 2015. Mineral Species Frequency Distribution Conforms to a Large Number of Rare Events Model: Prediction of Earth’s Missing Minerals. Mathematical Geosciences, vol. 47, no. 6, pp. 647-661; doi: 10.1007/s11004-015-9600-3
Grethe Hystad et al. Statistical analysis of mineral diversity and distribution: Earth’s mineralogy is unique. Earth and Planetary Science Letters, vol. 426, pp. 154-157; doi: 10.1016/j.epsl.2015.06.028
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