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Chao Kong

Next time you spot a vivid orange-yellow crust spreading across a rock in your garden, on a country wall or along a hiking trail, take a closer look – you might be standing on a fortune.
A Chinese research team has found that a humble lichen could serve as a visible field indicator of unknown rare earth deposits around the world.
The researchers said the lichen’s distinctive colour made it easy to spot on exposed rock, and the discovery could be combined with unmanned aerial vehicles and hyperspectral remote sensing to screen large areas for potential rare earth-bearing carbonates.
Chinese scientists have spent decades trying to identify biological indicators that could help locate mineral deposits.
“This is the second time Chinese scientists have discovered a similar indicator – the first was copper grass in the 1950s – and both are original scientific discoveries in mineral exploration,” said Professor Li Yang of Peking University and the Chinese Academy of Sciences on August 17.
The study, titled “Lichen as a Potential Exploration Tool for Rare Earth Element – Enriched Carbonatites”, was published in the peer-reviewed journal Economic Geology on July 27.
The lichen, Xanthoria elegans, grows preferentially on rare earth element-enriched carbonates.
Researchers found it on 57 of 67 carbonatite rocks mapped at the Bayan Obo mining area in northern China, the world’s largest rare earth deposit.


Although the lichen is widely distributed around the world, researchers found it was rarely present on granite, sandstone, quartzite and other non-carbonatite rocks.
The chance was typically below 1 per cent when it did occur on these rocks, according to the study.
“Once we find it, we can prioritise sampling, which significantly increases the probability of finding [rare earth deposits] compared with searching randomly,” Li said.
He said its brownish colour came from the organism itself rather than rare earth elements or iron. “That is why it is such a good indicator, because you can see it from far away.”
Chemical analysis provided further evidence of the link, with the lichen containing total rare earth elements of 3,500 to 17,000 parts per million.
Its rare earth content also increased with that of the underlying rock.
Lichens growing on more highly mineralised carbonates contained more rare earth elements than those growing on barren carbonates or altered surrounding rocks.

The researchers found tiny phases enriched in rare earth elements and barium inside the lichen’s organic material. This suggests that particles from the underlying rock may be incorporated during weathering and lichen-rock interactions.
“We believe that this lichen likes rare earth elements, but the specific biological mechanism is not yet clear,” Li said.
The finding does not mean the lichen actively seeks out rare earth elements. The biological and geochemical processes behind its elemental uptake remain uncertain.
The association is particularly strong at Bayan Obo, in China’s Inner Mongolia province, where the lichen preferentially colonises carbonates and areas affected by carbonatite-related alkaline alteration.
Early observations suggest the phenomenon may extend beyond Bayan Obo.
Li said colleagues working at elevations above 5,000 metres (16,404 feet) in the West Kunlun Mountains, southwest of Xinjiang, had reported a similar association after the paper was published.
Broader field studies are still needed to determine whether the lichen can reliably indicate rare earth mineralisation in other geological settings.


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Your backyard could hold a rare earth fortune – and this orange lichen is the clue

Lichen on rocks in the West Kunlun Mountains, southwest of China's Xinjiang Uygur autonomous region. Photo: Li Yang and team

Representative field photographs illustrating the restricted occurrence of lichen on non-carbonatite lithologies. Photo: Economic Geology 

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Clockwise from top centre are the rare earth oxides praseodymium, cerium, lanthanum, neodymium, samarium and gadolinium. Photo: USDA-ARS

News

China

Chinese scientists discover link between lichen growth and potentially untapped rare-earth-bearing carbonates and mineral deposits


Chinese scientists discover link between lichen growth and potentially untapped rare-earth-bearing carbonates and mineral deposits.


Xinjiang

Peking University

Chinese Academy of Social Sciences

Your backyard could hold a rare earth fortune – and this orange lichen is the clue

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}Chinese scientists discover link between lichen growth and potentially untapped rare-earth-bearing carbonates and mineral deposits

Chinese scientists discover link between lichen growth and potentially untapped rare-earth-bearing carbonates and mineral deposits