This set of Engineering Geology online test focuses on ” Formation and Descriptive Study of Minerals – 02″.
1. The mica group minerals show which structure in the microscopic level?
a) Box structure
b) Sheet structure
c) Hexagonal structure
d) Columnar structure
Explanation: The micaceous cleavage is explained by their atomic structure: they constitute of SiO4 tetrahedra linked at three of their corners and extending in two dimensions. This is called sheet structure.
2. There is presence of eminent cleavage in micas. State true or false.
Explanation: The sheets are held together in pairs by metallic ions. But the bond so resulting due to the metallic ions is the weakest and hence there is an eminent cleavage present in the micas.
3. What percent of crust do the micas form approximately?
b) More than 60%
Explanation: Micas are, besides felspars, pyroxenes and amphiboles, very common rock forming minerals forming approximately 4 percent of the crust of the Earth.
4. Which is the less important and more important and less important minerals crystallize respectively?
a) Triclinic and monoclinic
b) Monoclinic and triclinic
c) Monoclinic and rhombohedral
d) Rhombohedral and triclinic
Explanation: Most important members of the Mica group crystallize in one system only: Monoclinic system. Some less important members crystallize in triclinic system.
5. What type of cleavage is shown by mica group?
a) Perfect cubic cleavage
b) Perfect octahedral cleavage
c) Perfect basal cleavage
d) Prismatic cleavage
Explanation: The crystals of the mica group show prism angles of 60° and 120°. Because of atomic constitution, micas show excellent basal cleavage.
6. Which mineral is flaky and black in appearance?
a) Biotite mica
b) Muscovite mica
Explanation: Biotite mica is flaky and black in appearance and appears in the form of thin sheets. They are usually translucent.
7. What is the other name of muscovite mica?
a) Black mica
b) Potash mica
c) Vitreous mica
d) Glossy mica
Explanation: The other name of muscovite mica is potash mica and biotite mica is also called as black mica due its appearance.
8. What is the diaphaneity of muscovite mica?
d) Any form
Explanation: Muscovite mica usually occurs in the form of thin colourless sheets, as a mass may appear pale yellow and is transparent.
9. What is the streak given by muscovite mica?
Explanation: The colour of muscovite mica is usually colourless to pale yellow but gives no streak.
10. Pick the wrong statement about mica.
a) They have high hardness
b) They have low hardness
c) They are usually transparent to translucent
d) They are used as good electrical insulators
Explanation: The micas have low hardness of about 2.5 to 3. Hence the first statement is wrong. The rest of the statements about mica hold good.
11. What is the distinguishing property between biotite mica and muscovite mica?
Explanation: The colour of the minerals is the most distinguishing property between the two. The biotite mica shows black colour, whereas, the muscovite mica is almost colourless.
Sanfoundry Global Education & Learning Series – Engineering Geology.
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