When we think of wealth, gold is what comes to mind. After all, it is the universal symbol of money. However, recent research in Finland forces us to rethink what we believe about this inert mineral. According to scientists in Finland, they have just discovered that gold, in its nanoparticle form, is capable of circulating through the sap of red spruce trees.
Trees flecked with gold particles
The Kittilä gold mine is one of the largest producers in Europe. It is located in northern Finland, where researchers from the University of Oulu and the Geological Survey of Finland (GTK) set out to find the connection between flora and mineral deposits. And they succeeded: they were able to find gold embedded in the internal structure of the needles of red spruce trees (Picea abies).
Obviously, the amount of gold found in each tree is miniscule. It’s not as if King Midas had touched these spruce trees and they were now covered in gold. In fact, from a commercial point of view, it is not even economically viable to extract this gold from the trees. Scientists estimate that an entire tree would contain, at best, the equivalent of two euro cents in gold—barely 2¢.
These trees are not a direct source of wealth; their value is technological: the Norway spruce is a natural biosensor that can tell us where large hidden gold deposits are located.
How did scientists find out?
The discovery of red spruce trees filled with gold nanoparticles was no coincidence. This research process is called biogeochemical prospecting; this technique is based on the premise that plants act as biological pumps that extract and concentrate elements from the subsoil. As we all know, trees feed on the minerals they find in the soil and use sunlight to photosynthesise and live. Since they absorb nutrients from the soil, it was normal for them to also absorb a minimal amount of underground gold and be found in an area rich in this mineral.
This is why the researchers decided to analyse the foliage. They did not use a toy microscope, but one of the most advanced microscopes available today: a Field Emission Scanning Electron Microscope (FE-SEM). Together with X-ray Spectroscopy (EDS), this equipment not only allows tiny structures to be seen, but also identifies the chemical composition of each point.
As they found gold particles, these did not come from the surface, but were embedded within the cellular tissue of the needles. These particles were nanoparticles, measuring less than a millionth of a millimetre. This is why, although it is very nice to imagine, these red spruce trees do not have golden needles, but look like any other normal tree.
The alchemy of bacteria
As we have already mentioned, gold travels from the subsoil dissolved in water—as ions—to the leaves, but soluble gold is toxic to the plant. This is where a crucial solution comes into play: endophytic bacteria. These organisms live symbiotically and peacefully within the tree’s own tissues. Scientists conclude that these organisms are responsible for biomineralisation. They create a chemical environment that forces the gold to precipitate, and it ends up being encapsulated within the needle. Thus, the bacteria find a way to manipulate this metal and detoxify the tree that is their host.
The discovery of gold deposits in red moss could revolutionise the mining industry. Jazz, the search for mineral deposits often requires costly drilling that does not usually yield much. No, systematically planting red moss instead of taking soil samples is a much more natural and efficient way to survey the area without using heavy machinery.
For now, these bacteria that live in this symbiotic way are being analysed, as they could be used to develop mosses or specific materials that filter toxic heavy metals from contaminated water. We may not be able to have solid gold trees, but this discovery is still very lucrative for mining and ecological activities.