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prices rise sufficiently, the status of a previously unprofitable deposit changes, and it
becomes an ore. The status of unprofitable deposits may also change if a technological
advance allows the ore to be extracted at a lower cost than before.
Over the years, geologists have been keenly interested in learning how natural
processes produce localized concentrations of essential minerals. One well-established
fact is that occurrences of valuable mineral resources are closely related to the rock
cycle. That is, the mechanisms that generate igneous, sedimentary, and metamorphic
rocks, including the processes of weathering and erosion, play a major role in producing
concentrated accumulations of useful elements.

Task 5. Read the short note. Did you know about it?
Gypsum, a white-to-transparent mineral, was first used as a building material in
Anatolia (present-day Turkey) around 6000 BC. It is also found on the interiors of the
great pyramids in Egypt, which were erected in about 3700 BC. Today, an average new
American home contains more than 7 metric tons of gypsum in the form of 6000 square
feet of wallboard.

Test yourself

Task 1. Tell whether the sentences are true or false. Correct the false ones.
1. Rock-forming minerals and economic minerals are mutually exclusive groups.
2. Only eighty elements make up the vast majority of the rock-forming minerals and
represent more than 98 percent (by weight) of the continental crust.
3. Silicon and oxygen are by far the most common elements in Earth’s crust.
4. Silicon and oxygen readily combine to form the silicates.
5. It is impossible to indicate the conditions under which each silicate mineral is
formed.
6. The most common silicate minerals can be divided into two major groups on the
basis of their chemical makeup: the light silicates and the dark ones.
7. The dark silicates contain some amounts of aluminum, potassium, calcium, and
sodium rather than iron and magnesium.
8. The most common member of the pyroxenes group is augite.
9. Biotite has a shiny light appearance that helps distinguish it from the other dark
ferromagnesian minerals.
10. Both olivine and garnet have a glassy luster.
11. When calcite is the dominant mineral, the rock is called limestone.
12. Gypsum is the mineral name for common table salt.

Task 2. Using the geologic definition of mineral as your guide, determine
which of the items on the list are minerals and which are not. If not a mineral,
explain.
a. gold nugget b. sea water c. quartz
d. cubic zirconia e. obsidian f. ruby

g. glacial ice h. amber

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