Almost all Earth materials are used by humans for something. We require metals for making machines, sands and gravels for making roads and buildings, sand for making computer chips, limestone and gypsum for making concrete, clays for making ceramics, gold, silver, copper and aluminum for making electric circuits, and diamonds and corundum (sapphire, ruby, emerald) for abrasives and jewelry.
In this discussion, we hope to answer the following questions:
What constitutes a mineral resource and an ore?
What determines whether or not a mineral sources is economical to exploit?
By what processes do ores form?
How are mineral resources found and exploited?
What happens when a mineral resource become scarce as a result of human consumption?
What are the adverse effects of exploiting mineral resource.
Mineral resources can be divided into two major categories - Metallic and Nonmetallic. Metallic resources are things like Gold, Silver, Tin, Copper, Lead, Zinc, Iron, Nickel, Chromium, and Aluminum. Nonmetallic resources are things like sand, gravel, gypsum, halite, Uranium, dimension stone.
A mineral resource is a volume of rock enriched in one or more useful materials. In this sense a mineral refers to a useful material, a definition that is different from the way we defined a mineral back in Chapter 5. Here the word mineral can be any substance that comes from the Earth.
Finding and exploiting mineral resources requires the application of the principles of geology that you we have discussed or will discuss throughout this course. Some minerals are used as they are found in the ground, i.e. they require no further processing or very little processing. For example - gemstones, sand, gravel, and salt (halite). Most minerals must be processed before they are used. For example:
Iron is the found in abundance in minerals, but the process of extracting iron from different minerals varies in cost depending on the mineral. It is least costly to extract the iron from oxide minerals like hematite (Fe2O3), magnetite (Fe3O4), or limonite [Fe(OH)]. Although iron also occurs in olivines, pyroxenes, amphiboles, and biotite, the concentration of iron in these minerals is less, and cost of extraction is increased because strong bonds between iron, silicon, and oxygen must be broken.
Aluminum is the third most abundant mineral in the Earth's crust. It occurs in the most common minerals of the crust - the feldspars (NaAlSi3O8, KalSi3O8, & CaAl2Si2O8, but the cost of extracting the Aluminum from these minerals is high. Thus, deposits containing the mineral gibbsite [Al(OH)3], are usually sought. This explains why recycling of Aluminum cans is cost effective, since the Aluminum in the cans does not have to be separated from oxygen or silicon.
Because such things as extraction costs, labor costs, and energy costs vary with time and from country to country, what constitutes an economically viable deposit of minerals varies considerably in time and place. In general, the higher the concentration of the substance, the more economical it is to mine. Thus we define an ore as a body of material from which one or more valuable substances can be extracted economically. An ore deposit will consist of ore minerals, that contain the valuable substance. Gangue minerals are minerals that occur in the deposit but do not contain the valuable substance.
Since economics is what controls the grade or concentration of the substance in a deposit that makes the deposit profitable to mine, different substances require different concentrations to be profitable. But, the concentration that can be economically mined changes due to economic conditions such as demand for the substance and the cost of extraction.
