Answer: Tree Leaves

Searching for gold deposits is a costly and time consuming endeavor that mining companies do everything in their power to make more economical in pursuit of higher profits. Now, recent research has added a new high-tech tool to the toolbox of potential prospectors: atomic analysis of leaves.

After miners in Australia noted that the roots of eucalyptus trees often reached all the way down into veins of gold ore, researchers began investigating the possibility of analyzing trees to find evidence of gold deposits far below. Taking leaf samples and analyzing them is far more cost effective than conducting drilling and mining expeditions to locate ore, after all.

It turns out that you can, in fact, use the trees as gold detectors. The trees send their roots down deep in search of water and, in the process, pull up gold atoms from nearby deposits. Further, the plants push the gold atoms out to their leaves–presumably in an attempt to dispose of the heavy metal–and those leaves can easily be gathered and tested for the presence of gold.

When a mining company finds enough trees in a given area with gold atoms in their leaves, they can then confidently authorize a more extensive investigation of the area.