Researchers say that 208 of more than 5,200 officially recognised minerals are exclusively, or largely, linked to human activity, with crystals forming in locations as diverse as shipwrecks, mines and even museum drawers.
“This is a spike of mineral novelty that is so rapid – most of it in the last 200 years, compared to the 4.5bn year history of Earth. There is nothing like it in Earth’s history,” said Robert Hazen, co-author of the research from the Carnegie Institution for Science. “This is a blink of an eye, it is just a surge and of course we are only seeing the tip of the iceberg.”
In addition, the study points out that many more “mineral-like” substances, from laser crystals to components of concrete, have been devised and produced by human hands. “Human ingenuity has led to a host of crystalline compounds that never before existed in the solar system, and perhaps in the universe,” the authors write.
Together with the building of large-scale infrastructure and even human-related changes in the global distribution of minerals, including gemstones, the researchers argue that humankind is creating a defined layer in the geological record.
That, they add, backs up the burgeoning concept of the Anthropocene epoch – a new geological age that, while not yet confirmed by the International Union of Geological Sciences, is defined by the boom in human activity that has left a profound impact on the planet.
“That’s really I think the most important factor in deciding whether or not the Anthropocene is a new geological time period – the fact that we have created these materials, these crystals, that are incredibly diverse and beautiful and they persist through billions of years,” said Hazen. “They are going to be for ever on Earth, a distinctive marker layer that makes our time different from any other time in the preceding four and a half billion years.”
Published in the journal American Mineralogist by a team of researchers in the US, the new study reveals that 208 of the 5,208 minerals officially recognised by the International Mineralogical Association can be traced to human activity, although some, they note, can also form naturally. Among them is chalconatronite, a copper mineral that forms bright blue crystals and has been found on ancient Egyptian bronze artefacts.
Mining, and processes associated with it – such as mine fires, ore dumps and even mine timbers – have also been associated with the formation of unexpected substances. Among those found on mine tunnel walls are andersonite – a uranium-containing mineral that can emit a green fluorescent glow – and the copper-containing kornelite. “In many cases, mine tunnels have a very distinctive temperature and humidity that wouldn’t normally occur,” said Hazen. “A sharp-eyed collector will go into the mine and look at the walls with a magnifying glass and they’ll see these little crystals,” he added. “They never would have occurred if it hadn’t been for the fact that humans dug the tunnel.”
Abhurite, meanwhile, was found on the wreck of the unfortunately named SS Cheerful – a steamship that sank off the coast of Cornwall in 1885 – with the mineral, not known to occur naturally, formed from a reaction between seawater and the ship’s cargo of tin ingots.
But perhaps most serendipitous of all in its formation is calclacite. “[It] occurs in oak museum drawers because the minerals that are placed in the drawers react with the chemicals in the wood and you form a new mineral,” said Hazen. “That is just a crazy thing, you never would have expected it, and it would never occur if it hadn’t been for that kind of human activity.”
While all of the 208 crystalline substances in the new catalogue are officially recognised as minerals, since the mid-1990s the official definition has ruled out substances made by humans, meaning that many of those already in the record – and even more yet to be found – would no longer be classified as minerals. It’s a notion Hazen takes issue with, suggesting a new category is needed since many modern mineral-like materials, from laser crystals to components of cement, will also be adding to the complex array of novel minerals that archaeologists of the future might unearth.
“Imagine finding a solid waste dump where people throw away lots of computers and other electronic devices – you’ll have semiconductor chips and magnets and motors and all the metallic pieces and even speciality glasses with phosphors and so forth,” he said.
“In 100bn years, if someone comes back to Earth and looks at that land, they are really not going to be thinking ‘oh, this one is not a mineral or this one is a mineral’, they are just basically going to find these unusual crystalline compounds that form a distinctive marker layer,” Hazen added.
Jan Zalasiewicz, professor of palaeobiology at the University of Leicester and chair of the Working Group on the Anthropocene (WGA), said the new catalogue was an excellent study. “It does add significantly to the characterisation of the Anthropocene – not least because there is little that is more fundamental to rock strata than the minerals they are composed of,” he said.
While the exact onset of the Anthropocene is a moot point, with the dawn of thermonuclear weapons tests currently the favourite marker, Zalasiewicz says the new catalogue could also prove valuable in distinguishing the epoch.
“The WGA is now putting together a wide range of physical, chemical and biological data on the Anthropocene in preparation for a formal proposal to include it into the Geological Time Scale,” he said. “The features selected to define it will ultimately be those that provide the sharpest and clearest boundary for practical recognition by geologists. The mineral evidence will certainly be borne in mind as we’re considering this.”