Orange lichen points to rare earth rocks in China

A small orange crust on a rock may offer geologists a shortcut through difficult terrain. At the Bayan Obo deposit in Inner Mongolia, a team led by Professor Li Yang of Peking University and the Chinese Academy of Sciences found that Xanthoria elegans was strongly associated with rare-earth-bearing carbonatite rocks.

The lichen colonized 85 percent of the surveyed carbonatites. On granite, sandstone and quartzite — rocks that did not carry the targeted deposits — its occurrence fell to less than one percent. That contrast makes the organism a visible field proxy: prospectors could look for the orange-yellow growth before committing to more extensive geological surveys.

The signal is not only visual. As the rock beneath it weathers, microscopic particles of rare earth elements and barium become incorporated into the lichen's organic layers. Chemical analysis found rare earth concentrations of 3,500–17,000 parts per million, while strontium and lead isotope signatures closely matched those of the underlying carbonatite.

And then what? Survey teams could combine the lichen's color with hyperspectral cameras — sensors that identify material through reflected light — mounted on drones. That could help them bypass barren ground and concentrate fieldwork on areas with a stronger geological signal, offering the low-cost and lower-impact exploration method described by the researchers.

The limits are clear. Scientists still do not know why Xanthoria elegans prefers these rocks, and the link needs broader testing before it can be treated as a general prospecting tool. The South China Morning Post reported similar sightings in the West Kunlun Mountains, but the evidence so far comes from field research centered on Bayan Obo.