One classic view of geology held by many mining engineers is that there are only two types of rock; ore and waste. True enough, but deciding which is which is a task that requires skill and experience.
The first requirement is to locate the ore, i.e. the economically valuable material worth extracting. This in turn requires decisions as to what one needs to find.
In prehistoric times, these decisions were driven by defence against predators, hunting, heat, light, ornamentation and later, agriculture. Tools were made from stone (axes, clubs, scraping tools, knives, arrowheads). Settlement patterns often followed the availability of such materials; for example, populations were concentrated around sources of flint which was used extensively for cutting and shaping.
Early hominids found the materials they needed in river beds, on or near surface and on beaches. They sometimes followed the materials underground and/or by quarrying, but technology limited these activities to relatively shallow depths. The earliest known mines, from 43,000 years ago, are in Swaziland and were for the extraction of red ochre (iron ore) for pigmentation.
Subsurface disposition of rocks and minerals is studied using electrical, gravity and magnetic survey techniques known as geophysics; different rock types have different geophysical responses. Samples are taken from under the ground by drilling; these techniques can penetrate to depths of several kilometres. Data sets from these different activities are combined by computer to produce interactive maps and diagrams in Geographic Information Systems (GIS).
Mediterranean civilisations expanded rapidly through the discovery and use of copper, gold, silver and lead. Romans explored and mined across Europe and the resultant trade routes were the sinews of the Roman Empire. The lure of great riches of gold and silver spurred the exploration of the globe by European powers from the 1400’s onwards. Financed by sovereigns and by wealthy investors, expeditions led to precious metal discoveries in the Americas and in Africa and the creation of enormously wealthy European empires. Many new discoveries were in areas already developed by indigenous people whose technologies were less developed than those of the Europeans.
Approximately 70% of mineral discoveries are made by smaller or junior companies. They are typically financed by risk capital raised in stock markets. The process is similar to the “grubstaking” of gold prospectors in earlier centuries, whereby an investor would equip a prospector intent on making a fortune in unexplored parts of the world, in exchange for part of the resulting profits. Larger companies and sovereign states also invest in exploration, but seem to lack the agility and nimbleness of the smaller entities which must make discoveries in order to survive.
In quarrying, exploration has often been an “also ran”, with operators large and small content to expand operations at exiting sites without too much consideration as to what the expansion might entail. This approach is changing rapidly as the specifications for quarry products are increasingly stringent, requiring physical and chemical standards which require specialist skills in locating the right materials.
Notwithstanding the application of a wide range of scientific techniques, mineral exploration still needs a particular entrepreneurial mind-set; an ability to spot commodity trends, persistence and doggedness, an ability to deal with harsh conditions, poor logistics, suspicious governments and often sceptical communities. The neatest discovery can be derailed by unforeseen circumstances (e.g. a currency fluctuation, a commodity price collapse); a good explorer still needs a lot of that elusive commodity, luck.