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4. Because of their mobility, the ion-rich solutions can/must migrate great distances
through the surrounding rock before they are eventually deposited, usually as
sulfides of various metals.
5. Because these accumulations contain only 0.4 to 0.8 percent copper, between 125
and 250 kilograms of ore must/should be mined for every kilogram of metal
recovered.
6. However, the lava is usually able to / can move forward by breaking through the
hardened surface.

Discussion

Task 1. Read and memorize the following words:
olivine - олівін, хризоліт, перидот soil - ґрунт
biotite - біотит garnet - гранат
coating – шар, покриття luster - блиск
conchoidal – конкоїдальий, раковистий augite - авгіт
(про злам)
high-gloss – глянцевий pyroxene - піроксен
kaolinite - каолініт feldspar - польовий шпат
muscovite - калієва слюда, мусковіт clay - глина, глинозем
microcline- мироклин amphibole – амфібол, рогова обманка
opaque - матовий, без блиску; темний hornblende - амфібол, рогова обманка
orthoclase - ортоклаз

Task 2. Read the text. Translate it into Ukrainian. Talk about light and
dark silicate minerals. Use the following names of minerals in your story: olivine,
augite, hornblende, orthoclase, microcline, biotite, quartz, garnet, kaolinite.

Common silicate minerals
Most silicate minerals form when molten rock cools and crystallizes. Cooling
can occur at or near Earth’s surface (low temperature and pressure) or at great depths
(high temperature and pressure). The environment during crystallization and the
chemical composition of the molten rock determine, to a large degree, which minerals
are produced. For example, the silicate mineral olivine crystallizes at high temperatures,
whereas quartz crystallizes at much lower temperatures. In addition, some silicate
minerals form at Earth’s surface from the weathered products of other silicate minerals.
Still others are formed under the extreme pressures associated with mountain building.
Each silicate mineral, therefore, has a structure and a chemical composition that indicate
the conditions under which it formed.
The most common silicate minerals can be divided into two major groups on the
basis of their chemical makeup. The light (or nonferromagnesian) silicates are
generally light in color and have a specific gravity of about 2.7. The light silicates
contain varying amounts of aluminum, potassium, calcium, and sodium rather than iron
and magnesium. Here belong a feldspar group of minerals (the most common mineral
group which can be formed under a wide range of temperatures and pressures.
Orthoclase and microcline are common members), quartz (the only common silicate
mineral consisting entirely of silicon and oxygen), some minerals of the mica family of
minerals (with muscovite as a common member) and a group of clay minerals. Unlike
other common silicates, such as quartz and feldspar, most clay minerals originate as
products of the chemical weathering of other silicate minerals. Thus, clay minerals
make up a large percentage of the surface material we call soil. Because of the
importance of soil in agriculture, and because of its role as a supporting material for

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