This set of Engineering Geology Questions and Answers for Aptitude test focuses on “Important Sedimentary Rocks – 03”.
1. The non-clastic sedimentary rock chiefly made of carbonate of calcium is
Explanation: Limestones are the most common sedimentary rocks from the non-clastic group and are composed chiefly of carbonate of calcium with subordinate proportions of carbonate of magnesium.
2. Distinct texture shown by limestone is
c) Fossiliferous nature
d) Mud cracks
Explanation: In view of the diverse ways in which the limestones are formed, these rocks show a variety of textures. The most important texture feature of limestones is their fossiliferous nature.
3. Which type of limestone is non-marine is origin among the following?
d) Argillaceous limestone
Explanation: Kankar is a common nodular or concretionary form of carbonate material formed by evaporation of subsoil water rich in calcium carbonate just near the soil surface. It is non-marine in origin.
4. The major use of limestone is
a) Primary source material for manufacture of Portland cement
b) Used in metallurgical industries as flux
c) Used as building stone
d) Used as a source of magnesium
Explanation: Limestones and dolomites find important applications in many industries and engineering practice. Thus, limestone is a primary source material for manufacture of Portland cement and for a variety of limes.
5. What is a metamorphosed sedimentary rocks?
Explanation: Coal may broadly be defined as metamorphosed sedimentary rocks of carbonaceous character in which the raw material has mostly been supplied by plants of various groups.
6. The grade of coal with very low calorific value is
Explanation: Peat is the lowest grade coal that constitutes of only slightly altered vegetable matter. It may not be even considered as a coal. It has very low calorific value, high percentage of moisture and is rich in volatile matter.
7. The other name for brown coal is
Explanation: Lignite is also known as brown coal and forms the poorest grade of coal with calorific value ranging between 6.00-8300 B.th.U.
8. What is the hardness of lignite grade of coal?
Explanation: Lignite is compact and massive in structure with an upper specific gravity of 1.5 and hardness of 2.5 on Mohs’ scale of hardness. Some varieties of lignite may still show to a good extent the traces of original vegetable structure.
Explanation: Anthracite is considered the highest grade coal with fixed carbon ranging between 92-98 percent. It has highest calorific value in coals and burns without any smoke, as the volume matter is negligible.
10. A civil engineer has to deal with which rock in majority of cases?
a) Igneous rocks
b) Sedimentary rocks
c) Metamorphic rocks
d) Ultra-basic igneous rocks
Explanation: Sedimentary rocks cover a great part of the crust of the earth; they make up more than 75 percent of the surface area of the land mass. It is with these types of rocks that an engineer has to deal with in majority of cases. It is therefore, essential for a civil engineer to know as much as is possible about the salient features of these rocks.
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