The specific gravity of marble, is
⚖️ Understanding Specific Gravity
Specific gravity is a key indicator of a stone's quality. It's a measure of how dense the stone is compared to water. A higher specific gravity generally means the stone is denser, less porous, and stronger.
Specific Gravity (SG): The ratio of the density of a substance to the density of water. A stone with an SG of 2.72 is 2.72 times denser than an equal volume of water.
🔬 Detailed Analysis of Marble's Specific Gravity
D. 2.72
This is the correct answer. The standard, accepted value for the specific gravity of pure marble is 2.72. This value reflects its dense, crystalline structure, which is formed when limestone undergoes metamorphism. The process of metamorphism compacts the original limestone, increasing its density and therefore its specific gravity.
A, B, and C (2.50, 2.60, 2.66)
These values are closer to the specific gravity of various types of limestone, which is the parent rock of marble. Limestone's specific gravity typically ranges from 2.3 to 2.7. The value for marble is at the very high end of this range, reflecting the densification that occurs during its formation. While some sources may give a range for marble (e.g., 2.65-2.75), 2.72 is the precise textbook value to know for exams.
📊 Specific Gravity of Common Building Stones
| Stone Type | Parent Rock | Typical Specific Gravity |
|---|---|---|
| Marble | Limestone | 2.72 |
| Limestone | (Original Sedimentary) | 2.3 - 2.70 |
| Granite | (Igneous) | 2.6 - 2.70 |
| Basalt | (Igneous) | 2.8 - 3.0 |
💡 Study Tips
- Metamorphism = More Dense: Remember that marble is metamorphosed limestone. The process of metamorphism compacts the rock, making it denser. This is why marble's SG (2.72) is higher than that of most limestones.
- The "72" for Marble: Try to associate the specific number 2.72 with marble. It's a common value in civil engineering tests.
- Relate to the General Rule: A good building stone should have a specific gravity greater than 2.7. Marble, at 2.72, fits this rule perfectly, confirming its status as a high-quality (though soft) building material.