Correct Answer: C. metamorphic rocks
Solution:
Foliation refers to the parallel alignment of mineral grains in a rock, which gives it a layered or banded appearance. This texture is a direct result of the intense, directional pressure that occurs during metamorphism.
- Metamorphic rocks are defined by this alteration process, and foliation is one of their most common characteristics. Examples include slate, schist, and gneiss.
- Igneous and Sedimentary rocks do not form under these conditions and thus do not typically exhibit a foliated structure.
Correct Answer: B. diamond
Solution:
Hardness is measured on the Mohs scale from 1 (softest) to 10 (hardest). While technically a mineral, diamond is the hardest naturally occurring substance on Earth.
- Diamond: Ranks 10 on the Mohs scale, making it the hardest.
- Quartz: Ranks 7 on the Mohs scale.
- Marble: Ranks around 3-4 on the Mohs scale.
- Talc: Is the softest mineral, ranking 1 on the Mohs scale.
Correct Answer: A. soft
Solution:
For ornamental work, which involves intricate carving, shaping, and detailing, the stone must be soft enough to be worked by masons without fracturing. Hard stones are difficult to carve and are better suited for structural purposes where they need to resist high pressure.
Correct Answer: A. the presence of soluble matter of stone
Solution:
Smith's test is a simple field test to determine the presence of soluble, earthy substances in a stone sample. The procedure involves placing a piece of the stone in a glass of clear water and observing if the water becomes turbid or cloudy. If it does, it indicates the presence of soluble matter, suggesting the stone may have poor weathering qualities.
Correct Answer: D. metamorphic rock
Solution:
Limestone fits into several geological classifications, but it is fundamentally not a metamorphic rock.
- Sedimentary Rock: Limestone is a classic example of a sedimentary rock, formed from the accumulation of shells, coral, and other calcium-rich organic debris.
- Stratified Rock: Because it's formed in layers (strata), it is classified physically as a stratified rock.
- Aqueous Rock: Since it is formed from deposition in water, it is also known as an aqueous rock.
- Metamorphic Rock: This is incorrect. When limestone is subjected to heat and pressure, it transforms into Marble. Therefore, limestone is the parent rock, not the metamorphic rock itself.
Correct Answer: C. Basalt
Solution:
Volcanic rocks (also called extrusive rocks) are a type of igneous rock formed from lava that cools and solidifies on the Earth's surface.
- Basalt is the most common example of a volcanic rock.
- Granite is a plutonic (intrusive) rock, formed deep within the crust.
- Dolerite is a hypabyssal rock, cooling at intermediate depths.
Correct Answer: A. right angles
Solution:
Stratified rocks have natural layers or "beds" which are planes of weakness. To ensure maximum strength in masonry, the stone should be placed so that the load (pressure) is applied perpendicular (at right angles) to these bedding planes. This prevents the stone from splitting along its natural layers.
Correct Answer: C. Calcareous rock
Solution:
The chemical classification of rocks is based on their main component. Calcareous rocks are those that are predominantly composed of calcium carbonate (CaCO₃). Limestone and marble are the most common examples.
Correct Answer: C. Volcanic rocks
Solution:
Volcanic rocks, also known as extrusive igneous rocks, are formed when magma erupts onto the Earth's surface (as lava) and cools quickly. This rapid cooling prevents the formation of large crystals.
- Plutonic rocks form deep underground from slow cooling.
- Hypabyssal rocks form at intermediate depths.
- Igneous rocks is the general category for all rocks formed from magma, but "Volcanic" is the specific term for surface cooling.
Correct Answer: D. All the above
Solution:
This question covers the concept of the "natural bed" of a stone, which is crucial for masonry work.
- A: This is the definition of the natural bed – it's the original plane of formation, which is often the weakest plane.
- B: In sedimentary rocks, the natural bed corresponds directly to the layers (strata) in which the sediment was deposited.
- C: Igneous rocks form from molten magma and lack a layered structure, so they do not have a defined natural bed.
Since all three statements are correct, "All the above" is the right answer.
Correct Answer: D. All the above
Solution:
Blasting is a method used to quarry large quantities of hard stone. The resulting irregular fragments are not suitable for fine masonry but are ideal for applications where bulk and strength are needed. These include:
- Ballast in railways: To provide a stable bed for railway tracks.
- Aggregates for concrete: As the primary filler material in concrete mixes.
- Road metal: For the base layers of roads and pavements.
Correct Answer: C. radial
Solution:
In an arch, the forces are transferred along the curve of the arch down to the abutments. To ensure the stone's maximum strength, its natural bedding planes must be oriented to be perpendicular to the direction of this thrust. Placing the stones so their bedding planes are radial (pointing towards the center of the arch's curve) achieves this, making the arch strong and stable.
Correct Answer: D. heavy
Solution:
Retaining walls work by using their own weight and mass to hold back soil. Therefore, the stones used must be heavy to provide the necessary stability and resist the lateral pressure from the earth they are retaining.
Correct Answer: D. 2.7
Solution:
Specific gravity is a measure of a stone's density. A higher specific gravity indicates a denser, less porous stone, which is generally stronger and more durable. For a high-quality building stone suitable for structural use, the specific gravity should generally be greater than 2.7.
Correct Answer: D. 2.72
Solution:
The specific gravity of building stones varies depending on their mineral composition and porosity. Marble, being a dense, recrystallized limestone, has a specific gravity that typically falls in the range of 2.70 to 2.75. The most commonly cited average value is 2.72.