SCANNING: Earth’s building blocks (R.P – 4.2)
3.1.1 Pay attention to the pronunciation of the following minerals: Which minerals have the same translation in both languages and which do not?
| hematite | magnetite |
| dolomite | halide |
| mica | fluorite |
| feldspar | halite |
| carbonate | hydroxide |
| quartz | limonite |
| asbestos | brucite |
| calcite | sulfate |
| aragonite | gypsum |
| galena | phosphates |
| silicate | apatite |
| oxide | monazite |
| sulfide | tungstate |
| pyrite | wolframite |
3.1.2 Find the information you need to complete the following diagram from the text below.
ROCK-FORMING MINERALS
| mineral |
| abundance |
| composition |
| examples |
Rocks are mixtures of minerals. Most rocks consist of interlocking grains or crystals stuck together by natural cement. A few dozen minerals provide the main ingredients for the most common rocks. Here are brief details of some rock-forming minerals.
1. Silicates are the chief rock-forming minerals. Most features a metal combined with silicon and oxygen. Examples: asbestos, mica, and feldspar.
2. Carbonates, the second most abundant group of minerals, include carbon, oxygen and one or more metals. Examples: calcite, dolomite and aragonite.
3. Sulfides are compounds of sulfur and one or more metals. Examples: galena and pyrite.
4. Oxides are compounds of oxygen and one or more metals. Examples: quartz, hematite and magnetite.
5. Halides are compounds of a halogen and a metal. Examples: fluorite and halite (rock salt).
6. Hydroxides are compounds of hydrogen, oxygen and usually a metal. Examples: limonite and brucite.
7. Sulfates are compounds of sulfur, oxygen and a metal. The commonest sulfate is gypsum.
8. Phosphates are chemical compounds related to phosphoric acid. Examples: apatite, monazite.
9. Tungstates are salts of tungstic acid. Example: wolframite (a tungsten ore).
(Lambert “The Field Guide to Geology” 1988, Cambridge University Press)
| CHEMICAL CLASS | MINERAL NAME | CHEMICAL FORMULA | |
| NATIVE ELEMENTS | Native copper | Cu | |
| Gold | Au | ||
| Sulfur | S | ||
| Graphite | C | ||
| Diamond | C | ||
| OXIDES and HYDROXIDES | Quartz | SiO2 | |
| Hematite | Fe2O3 | ||
| Magnetite | Fe3O4 | ||
| Corundum | A12O3 | ||
| SULFIDES | Pyrite | FeS2 | |
| Chalcopyrite | CuFeS2 | ||
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SULFATES
CARBONATES
PHOSPHATES
SILICATES
MICA GROUP
FELDSPAR GROUP
Table 2. Chemical Grouping and Composition of Some Common Minerals
Complete the following chart. Give examples of each type of rock forming mineral.
| silicates | oxides | sulfides | carbonates | sulphates | phosphates |
INFORMATIVE READING- Minerals and their physical properties.
3.2.1 Read the following text and answer the questions. (R.P – 4.7)
PART 1 Minerals
Minerals are the fundamental building blocks of rock materials in the earth. They are defined as naturally occurring inorganic substances with a definite chemical composition and specific crystal structure. Over 2000 minerals have been identified in the Earth. There are over 100 elements in the crust, which consists almost entirely of eight elements. The remaining elements account for less than 1% of the crust, which therefore has a very simple composition.
The first eight elements are the most common and constitute the basic ingredients for most continental crustal rocks, which are predominantly are silicates and to a lesser extent oxides.
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Main Elements in the Continental Crust
| Element | Weight Per cent | Atom Per cent | Volume Per cent |
| Oxygen | 46.40 | 62.17 | 94.05 |
| Silicon | 28.15 | 21.51 | 0.88 |
| Aluminum | 8.23 | 6.54 | 0.48 |
| Iron | 5.63 | 2.16 | 0.48 |
| Calcium | 4.15 | 2.22 | 1.19 |
| Sodium | 2.36 | 2.20 | 1.11 |
| Magnesium | 2.33 | 2.05 | 0.32 |
| Potassium | 2.09 | 1.15 | 1.49 |
| TOTAL | 99.34 | 100 | 100 |
As minerals are defined by composition and by crystal structure, these two parameters must be consistent to result in the predictable constancy of each mineral. Crystal structure is controlled by composition that directly determines the arrangement of atoms. Some minerals can occur in several polymorphs (physical forms), so some of the physical properties expected for one particular polymorph will not apply to another form. At the same time, some physical characteristics have a sufficiently wide range may be non-diagnostic by themselves, but will be indicative when combined with other features. (General Geology. Textbook. Part 1-Tomsk: TPU Press, 2004)
1. What are minerals?
2. How many minerals are in the earth?
3. What are the main elements in the continental crust? Enumerate them.
4. What are the two parameters of minerals?
5. What is the main characteristic feature of crystal structure?
PART 2
3.2.2 Read the text and fulfill the after-reading exercises. (R.P – 4.3, 4.6) Physical Properties
Physical properties of minerals are often the only guidelines for field identification of specimens that may occur combined with other minerals or in very small amounts in a particular sample.
1. Minerals grow into consistent crystal shapes, which are controlled by the chemical composition of the minerals. There are six crystal systems that include all minerals. Some mineral compounds can form more than one mineral with entirely different crystal structures. Some examples of the crystal form are:
• isometric,
• elongated,
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• flattened.
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