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repetitive – той, що повторюється secrete - виділяти
Task 2. Read the text. Translate it into Ukrainian. Talk about the major
characteristics of minerals. Transcribe the following words: calcium carbonate,
crystalline, mercury, obsidian, chemical formula, quartz, silicon, oxygen, ratio.

Characteristics of minerals
Geologists define mineral as any naturally occurring inorganic solid that
possesses an orderly crystalline structure and can be represented by a chemical
formula. Thus, Earth materials that are classified as minerals exhibit the following
characteristics:
1. Naturally occurring. Minerals form by natural, geologic processes. Synthetic
materials, meaning those produced in a laboratory or by human intervention, are not
considered minerals.
2. Solid substance. Only solid crystalline substances are considered minerals.
Ice (frozen water) fits this criterion and is considered a mineral, whereas liquid water
and water vapour do not. The exception is mercury, which is found in its liquid form in
nature.
3. Orderly crystalline structure. Minerals are crystalline substances, which
means their atoms are arranged in an orderly, repetitive manner. This orderly packing of
atoms is reflected in the regularly shaped objects called crystals. Some naturally
occurring solids, such as volcanic glass (obsidian), lack a repetitive atomic structure
and are not considered minerals.
4. Generally inorganic. Inorganic crystalline solids, such as ordinary table salt
(halite), that are found naturally in the ground are considered minerals. (Organic
compounds, on the other hand, are generally not. Sugar, a crystalline solid like salt but
which comes from sugarcane or sugar beets, is a common example of such an organic
compound.) Many marine animals secrete inorganic compounds, such as calcium
carbonate (calcite), in the form of shells and coral reefs. If these materials are buried
and become part of the rock record, they are considered minerals by geologists.
5. Can be represented by a chemical formula. Most minerals are chemical
compounds having compositions that can be expressed by a chemical formula. For
example, the common mineral quartz has the formula SiO 2, which indicates that quartz
consists of silicon (Si) and oxygen (O) atoms in a ratio of one-to-two.

Task 3. Look at Figure 11.1. What does the diagram illustrate? What
characteristic feature of minerals does it refer to?

Task 4. List five characteristics an Earth material should have in order to
be considered a mineral.

Task 5. Based on the definition of a mineral, which of the following
materials are not classified as minerals, and why: gold; water; synthetic diamonds;
ice; and wood.

Task 6. Imagine that you are a teacher. How would you explain the major
characteristic features of minerals to the students? Present a small dialogue.

Task 7. Discuss the following characteristics of the Earth materials that are
classified as minerals:
1. Naturally occurring minerals.
2. Minerals that are solid substances.
3. Minerals with orderly crystalline structure.
4. Generally inorganic minerals.

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