According to the World Gold Council, over 174,000 tons of gold have been mined from the Earth since the early periods of civilization. In 2011, the United States Geological Survey estimated that there are still 51,000 tons of gold being reserved on our planet.
As the first metal discovered by humans, gold holds a central position in human history. At present, gold remains one of the dominant factors influencing the global economy and the lives of individuals.
The topic of gold mining is of great interest as the reserves of this precious metal are gradually declining. However, in a study conducted nearly a decade ago, scientists discovered gold stored in trees, which has surprised many regarding the identity of the tree species.
Gold Found in Eucalyptus Leaves
Australian researchers found that tiny gold particles from underground ore deposits are present in eucalyptus leaves. Most plants root deeply into the Earth, absorbing nutrients and minerals essential for life. Therefore, many hypotheses suggest that in the process, the trees inadvertently “absorb” gold.
The eucalyptus tree has the ability to transport ultra-small gold particles from deep mines due to its remarkably long root system. The roots of Eucalyptus marginata—belonging to the Eucalyptus genus in the Myrtaceae family—can penetrate up to 40 meters into the ground in search of water in arid areas. In this process, the tree roots may collect other elements, such as gold.
In 2019, Marmota discovered gold in South Australia using a method that employs trees to detect underground minerals. Marmota identified a gold vein 6 meters thick, containing 3.4 grams of gold per ton, located about 44 meters deep. This is a notable discovery since this mine is at least 450 meters away from other known gold mines.
Verifying the Truth
To verify whether eucalyptus trees can “absorb” gold, researchers investigated the leaves, branches, and bark of eucalyptus trees up to 10 meters tall from two locations in Australia—one in the west and one in the south. Previous drilling indicated that these sites contained gold buried underground. These areas were not disturbed by mining activities, allowing for the exclusion of the possibility of gold dust remaining on the leaves.
Scientists believe that tiny gold particles from underground ore deposits are present in eucalyptus leaves.
They also grew eucalyptus trees in a greenhouse with soil mixed with gold particles, as well as in normal soil without gold for comparison.
X-ray analysis revealed gold particles measuring up to 8 microns in the cells of the trees, or about 10 times thinner than an average human hair. Both field samples and greenhouse experiments showed that these gold particles—existing at concentrations harmless to the tree—are absorbed by the roots and transported to various parts of it, with the leaves exhibiting the highest concentrations of gold.
The average concentration of gold in the leaves is only about 46 parts per trillion, equivalent to 0.000005% of the weight of each leaf.
The lead author of the study, Melvyn Lintern, a geochemist at the Commonwealth Scientific and Industrial Research Organisation in Australia, stated: “We were very surprised by the ability to carry gold from a height equivalent to a 10-story building in eucalyptus trees.”
The researchers do not suggest extracting gold from these eucalyptus trees, as Lintern cautions: “The amount of gold in the tree is extremely low. It is estimated that it would take about 500 eucalyptus trees to gather enough gold to make a ring.”
Nonetheless, this discovery is still highly regarded by experts for its potential. Instead of becoming a tool for gold mining, eucalyptus trees could help miners locate potential deposits deep within gold mines, thereby avoiding the waste of time, money, and resources searching for precious metals across vast areas, Lintern added.
Little-Known Facts About Eucalyptus Trees
Not only do eucalyptus trees serve as “gold absorbers,” but they also possess many unusual characteristics. Here are some interesting facts about this familiar tree:
Eucalyptus Flowers Lack Petals
From a distance, the flowers on most eucalyptus trees look like clusters of dandelion seed heads. Upon closer inspection, you’ll notice that these flowers lack petals. The entire “flower” is actually a collection of hundreds of stamens emerging from a cone-shaped bud in the center.
These flowers do not have petals.
Eucalyptus trees need to produce as much pollen as possible. They have few natural pollinators due to their high cineole concentration. Typically, these trees are self-pollinating.
Cineole: The Secret Ingredient
Eucalyptus oil has been used in Australian indigenous medicine as an antibacterial and antifungal agent for centuries. In Indian medicine, it is often utilized to treat respiratory illnesses. In 17th century England, eucalyptus oil was used to disinfect hospitals.
This is because the leaves and bark of the tree contain high levels of cineole. Cineole is a colorless liquid organic compound. Sometimes referred to as eucalyptol, it is abundant in eucalyptus and related shrubs. The fragrance of eucalyptus primarily comes from the scent of cineole.
Only koalas, ring-tailed possums, and a few insect species can consume eucalyptus leaves and bark. No other creatures, including humans, can tolerate high levels of cineole. This is why it serves as an effective and natural insect repellent.
Clinical studies have demonstrated the antibacterial, disinfectant, and antifungal properties of cineole. Eucalyptus oil is particularly effective for treating topical wounds, skin care, and disinfection.
Eucalyptus Trees Help Reduce Malaria Incidence
Because the tree’s essential oils repel insects, eucalyptus is planted in areas with high malaria rates.
Malaria is a disease found on every continent. The malaria parasite lives in female mosquitoes that bite humans and is transmitted to people when bitten. In areas with high malaria-carrying mosquito populations worldwide, eucalyptus planting has been adopted to help mitigate this issue.
Eucalyptus Trees Can Help Manage Wastewater Issues
Over the years, scientists have been researching the use of eucalyptus to mitigate wastewater issues. In some parts of the world, wastewater carrying heavy metals, bacteria, and other toxins poses a concern for agriculture.
Environmental engineers and forestry experts plant eucalyptus trees in polluted locations. There is substantial evidence that eucalyptus trees absorb and filter numerous harmful elements present in the water used for irrigation.
Although more research is needed to determine the appropriate balance of these trees with agricultural land, experts consider this a promising and feasible solution.
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