If you’re looking for gold, look in trees

IN THE GOOD old days, gold miners could seek out visible specks of bling at the surface in order to find deeper, richer veins. These days, prospectors must examine samples of dirt for more minute traces suggestive of a hidden seam below. Analysing water from boreholes can also yield clues, but boreholes are scarce and new ones are costly and time-consuming to drill.Trees offer an alternative that is finally bearing fruit in Australia. The idea has been around since the 1940s but, until now, never practical. Some trees have roots that reach deep underground, drawing up water and, along with it, tiny quantities of minerals that end up distributed throughout the tree. In this way, even lofty leaves bear traces of what lies far beneath. The quantities are minuscule. In areas where there is no gold, leaves may have a background level of 0.15 parts per billion (ppb) of gold; on gold-rich sites that can rise to 4ppb.