Which of the following methods of quarrying is suitable for quarrying small, thin and regular blocks of stones from rocks such as granite and gneiss?
- AExcavating
- BBlasting
- CWedging
- DHeatingCorrect
Solution
Concept
In the heating method, rock is heated and then cooled, so thin layers split off. It is used for granite and gneiss.
Step-by-step solution
1. Recall the quarrying methods: excavating, wedging, heating and blasting. 2. Excavating is used for soft stones or stones buried in earth. 3. Wedging is used for stratified rocks like sandstone, limestone and marble. 4. Blasting is used for hard, compact rocks and produces large, irregular pieces. 5. Heating gives small, thin and regular blocks from granite and gneiss. 6. Answer: (D) Heating.
Explanation
Wood or fuel is burnt on the rock surface. The top layer expands more than the rock below, so it separates from it. Sudden cooling helps the split, which gives thin, regular blocks of granite or gneiss.
Why the other options are wrong
A: Excavating is for soft stones, not hard granite. B: Blasting gives large, irregular blocks. C: Wedging is for rocks with natural layers, like sandstone and marble.
Shortcut
Thin regular blocks from granite or gneiss = Heating.
Common mistake
Choosing blasting because granite is hard. Blasting does not give thin, regular blocks.
Correct answer: D) Heating