If you thought your rock and mineral collection was reasonably complete, guess again.
A team of researchers, led by the Carnegie Institute for Science's Robert M. Hazen, used a sophisticated statistical modeling system to calculate that the Earth has a lot of undiscovered minerals - 1,563, to be precise - to add to the nearly 5,000 that already are known. Moreover, the scientists predict that Earth's mineral diversity is unique, and is not duplicated anywhere else in the universe - even on Earth-like rocky exoplanets.
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Those findings are contained in an quartet of recently published articles in Canadian Mineralogist, Mathematical Geoscience, American Mineralogist, and Earth and Planetary Science Letters.
Minerals are naturally occurring, inorganic substances that are crystalline - that is, have an ordered arrangement of atoms - and definite chemical compositions. They can be formed with the help of a variety of different types of geological activity, ranging from volcanoes and plate tectonics to water-rock interactions, as well as by biologically-based chemical reactions.
The latter are particularly important, according to Hazen, who has long theorized the Earth's diversity of minerals is related primarily to the development of life on this planet. More than two thirds of known minerals can be linked directly or indirectly to biological activity, such as the carbonate minerals created by freshwater bacteria. The rise of bacterial photosynthesis 2.4 billion years ago, which dramatically increased the atmosphere's oxygen concentration, also expanded the number of mineral species.
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Hazen and his colleagues used statistical models of ecosystems and compared them to mineralogical databases in order to predict that thousands of mineral species that have been created during the Earth's history. Some have been lost due to burial, erosion or subduction back into the Earth's mantle, but by the team's calculations, 1,563 of them still exist and are waiting to be discovered.
Another weird fact: Most of the earth's mineral types are rare, and found at five or fewer locations on the planet.