Mapping the occurrences of minerals is the basic building block to a well-executed geological program. Actually it is not the minerals themselves that are mapped but the different types of rocks that are exposed on the surface of the earth that are mapped. The bearded ones have an infinite variety of funny names for different types of rocks and every type has sub-groups and sub-sub-groups etc. When a geologist gets going his eyes will often glaze over and his vocabulary will go from the sublime to the arcane. Actually it is the eyes of the listening, non-geologist which glaze over. Nor do I think most geologists understand what they are saying.

Nevertheless, rocks have been classified six ways from Sunday including; colour, crystal size, texture, age, how it was born and several other interesting categories. When a geologist happens across a bunch of rocks sticking out of the ground he instinctively wants to “map” them. That is, depending upon the age of the geologist, he will pull out either a sophisticated compass or an electronic global positioning system (GPS) and write a bunch of notes about the rock. “Spotted an exposure of greenish-pink greywackies striking to the NNE 35 degrees with a textural dip of minus 47.5 degrees. Noted several instances of clasts of brownish purple leached andesitic altered potassic granites. Probably of Upper Cretaceous age” He will then hurry back to his home, plot the outcropping rocks on the topographic map that he bought from Maptown and then pull out the best part of the geologist’s kit... his coloured pencil crayons. The outlines on the map will be coloured based on origin and age of the rocks and the map will be given a legend that is supposed to explain it all. And if you have ever wondered why the part that explains a map is called a “legend” then you have never seen a geological map. To the uninitiated, the whole thing looks make-believe. But it does look very cool and, in fact, is very useful in trying to figure out what happened to those rocks millions of years ago.

Not only the rocks are mapped but also the structures that caused the rocks to be there. These are things called faults, folds, fractures, anticlines, synclines etc. To confuse the layperson these things are called “tectonic events” and trying to figure them out is like looking at a car that hit a wall at 150 miles per hour to determine which fold in the hood occurred first. It is one hundred percent conjecture but is fun in its own way. So the good geologist will put lines on his map showing the direction of the fault and the angle at which it tilts into the earth. Often the rocks on one side of a fault are different from those on the other side so they will guess which side moved up and which side moved down. This is all magic and one has to go to a special geology magic school to understand it but it seems to work.

So that is mapping. It is painstaking work and arguably the most important part of geology - at least mineral geology. Get the map wrong and it will throw off any attempts to understand how the rocks were formed and whether there is any hope of finding minerals in the rocks. Get it right and as more detailed information is made available from sampling, geophysics and drilling things will fall into place quite nicely. Normally, though when a map is correctly made you are left with a very elegant bit of artwork that says you have found absolutely nothing of value. Having mapped the rocks then you have to take some samples of them to put on your living room shelf. And you thought the wives of engineers were long suffering.