2.22 From ancient peoples to modern mines
But what about modern mines?
Finding sources of metals can be done in a number of ways. Geologists can recognise minerals or specific rock types that they know contain the metal or element they are looking for. This can involve many weeks or months of studying aerial or satellite photographs, and then going out into the countryside (or ‘the field’, as geologists call it) to hunt for evidence and collect rock samples. These are then brought back to the laboratory for analysis and the percentage of different elements can be worked out.
But normally it is a combination of methods. There are more indirect routes that don’t look at the elements in the rocks themselves but measure them in the water of streams and rivers.
The ‘concentration’ (amount per unit volume or mass) of metals that are found dissolved in stream and river water will increase as you get closer to the source rock which contains them. This means that geologists can plot maps showing these concentrations that tell us where might be the best place to find metals.