Scientists have identified a sudden explosion of mineral diversity on the surface of our planet that would not exist if it weren't for humans, adding weight to the argument that we're living in a new geological epoch - the Anthropocene.
A new study has found that the incredible upsurge of new minerals around the time of the industrial revolution led to the unprecedented diversification of crystals on Earth, eclipsing even the Great Oxidation Event 2.3 billion years ago as the "greatest increase in the history of the globe".
"This is a spike of mineral novelty that is so rapid - most of it in the last 200 years, compared to the 4.5-billion-year history of Earth. There is nothing like it in Earth's history," one of the team, Robert Hazen from the Carnegie Institution for Science told The Guardian.
"This is a blink of an eye, it is just a surge, and ... we are only seeing the tip of the iceberg."
Hazen and his team analysed the 5,208 minerals on Earth that are officially recognised by the International Mineralogical Association, and found that 208 of them would not exist if it weren't for human activity.
These human-triggered minerals include chalconatronite, a rare copper mineral that crystallises as a bright blue crust on ancient Egyptian bronze artefacts, and andersonite, a uranium-laced mineral with a fluorescent green or yellow glow that forms on the walls of mine tunnels.
The bronze-hued abhurite was discovered on the wreck of the SS Cheerful, which sank off the coast of Cornwall, England in 1885, and only formed because of a chemical reaction between the salt water and the ship's sunken supply of tin ingots.
Most of the 208 minerals triggered by humanity came about thanks to mining, while six were found on the walls of smelters, three in a geothermal piping system, and four on prehistoric sacrificial burning sites in the Austrian mountains.
Many other new minerals could also be forming in our giant waste dumps, encrusting old batteries and electrical appliances like never before, the team suggests.
"There are probably all sorts of things forming as a result of old silicon chips or batteries," Hazen told Chelsea Whyte from New Scientist.
"TVs have all these exotic phosphors they use, and magnets and all sorts of high-tech materials. When you start hydrating and oxidising them, you're going to start finding a lot of exotic new materials."
The list did not include new minerals that have been deliberately synthesised by humans, such as those produced in magnets, batteries, and synthetic gemstones, as the 'true' definition of a mineral according to the International Mineralogical Association is that it must occur "naturally".
Over the course of Earth's history, the team found that most minerals on Earth appeared very gradually during the Great Oxidation Event, which began roughly 2.3 billion years ago, and could have lasted as long as until 1 billion years ago.
The event saturated Earth with atmospheric oxygen for the first time, thanks to an explosion of photosynthetic bacteria, and the minerals on the surface increased from just over 2,000 varieties to more than 4,000.
While this event gave rise to around two-thirds of the 5,208 mineral types officially recognised today, that gradual build was nothing compared to the sudden burst of diversity that's occurred over the past few centuries.
Since the mid-1700s, the diversity of minerals on Earth has exploded faster than ever before, the team noting the "blazing pace" that humans triggered over the past 250 years - especially when compared to the slow burn of the Great Oxidation Event.
They say this unprecedented diversification is the fastest rate of new mineral production in Earth's history, and a clear marker of a new geological epoch caused by humans - the much-debated Anthropocene.
"To imagine 250 years relative to 2 billion years, that's the difference between the blink of an eye ... and one month," Hazen says in a press statement.
"Simply put, we live in an era of unparalleled inorganic compound diversification. Indeed, if the Great Oxidation eons ago was a 'punctuation event' in Earth's history, the rapid and extensive geological impact of the Anthropocene is an exclamation mark."
The Anthropocene has yet to be officially recognised, but scientists have been arguing for years that human influence on the planet has been so dramatic, it will be clearly defined in Earth's strata - layers of sedimentary rock or soil that delineate major geological events in our planet's history.
Hazen and his team now say that this explosion of new minerals has to be considered by the International Commission on Stratigraphy - the group that will ultimately decide whether or not to reorganise the Anthropocene - as a serious marker of a new epoch.
"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," Hazen told Nicola Davis at The Guardian.
"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 4.5 billion years."
Previous arguments for the Anthropocene suggest that humans cut short the 11,700-year-old Holocene epoch in 1950, when nuclear tests created a new stratum in Earth's surface.
Or it could have started in 1610, when a dramatic drop in atmospheric CO2 levels, triggered by the arrival of Europeans in the Americas in 1492, was captured in the Antarctic ice-core records.
This new study is more solid evidence of human influence on the planet, Hazen and his team argue.
"If you're a geologist who came back 100,000 years or a million or a billion years from now ... you would find amazing mineralogical evidence of a completely different time," Hazen told The Washington Post.
We'll have to wait and see if their argument is strong enough.
The research has been published in American Mineralogist.