Jul 10, 2022 - Science

Study: Nature used 57 ways to make over 5,600 minerals on Earth

calcite
Calcite. Photo: Rob Lavinski

Nature uses 57 ways to make the more than 5,600 minerals on Earth, scientists reported earlier this month.

Why it matters: Minerals are currently classified by their structure and composition — what they are. Adding information about how and when a mineral formed could help scientists spot signs of life on other planets and understand the origins of it here on Earth.

  • "If you want to know the past of Earth, then these are the time capsules, and we can open them with the information that they contain," mineralogist Robert Hazen of the Carnegie Institution for Science said, holding a more than 4.5 billion-year-old meteorite found in Morocco in his hand. In it, there are grains of minerals formed more than 5 billion years ago — before our solar system.

Details: Hazen and Shaunna Morrison, also of the Carnegie Institution of Science, compiled research about how the minerals recognized by the International Mineralogical Association formed — under high or low temperatures, with or without water, with an assist from microbes or not.

  • They found nature has 57 ways to make minerals — some involving lightning, penguin urine, microbes, volcanoes, plate tectonics, stars and more.
  • About 60% of the minerals found on Earth form one way, and 24% can form in two ways.
  • But nine minerals can be made in more than 15 ways. There are 21 paths to pyrite (fool's gold) — the most of any mineral.
  • Under their system, which is detailed in two recently published papers in the journal American Mineralogist, there are more than 10,550 "mineral kinds" on Earth. They say the classification system — the culmination of 15 years of work for Hazen — is a complement to the existing one.

They also found water is key. It helped to form more than 80% of minerals. Biological processes had a role in forming about half of minerals.

  • Knowing the markers of a mineral produced by microbes or water could help scientists spot those signs of life in the minerals of other worlds.

The intrigue: More than 42% of minerals are formed with the involvement of rare elements, which are less than 5 parts per million of Earth's crust.

  • That suggests Earth "has an incredible ability to select and concentrate rare elements through water-rock interactions," Hazen said, adding those interactions give "an incredible burst of diversity."
  • Mars has a ratio of rare elements similar to Earth. But Earth has plate tectonics and water that concentrate those elements and form minerals, said Morrison, who studies the mineralogy of Mars. "So we started out with the same stuff, but ended up in pretty different places."
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