--- title: "Properties and uses of granite, phyllite, limestone" subject: "Engineering Geology I" chapter: 4 key: "semester_3/engineering_geology_i:properties-and-uses-of-granite" source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/properties-and-uses-of-granite site: BCT Engineering --- # Properties and uses of granite, phyllite, limestone Engineering Geology I · Chapter 4: Petrology - Asked in: 2081 Chaitra (new course), 3×2 marks; 2074 Chaitra, 6 marks; 2074 Asoj, 3 marks; 2069 Chaitra, 3 marks (asked 4 times) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/properties-and-uses-of-granite - Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-4 ## Question Describe the physical properties, engineering properties and engineering uses of granite, phyllite and limestone. ## Short answer Granite is coarse-grained, strong (100–250 MPa), durable, used for foundations, building, aggregates. Phyllite is fine-grained, foliated, weak (20–60 MPa), anisotropic, prone to landslides, used for roofing slabs. Limestone is soluble (karst), strength 30–150 MPa, used for cement and aggregate. ## Answer #### Granite (igneous, intrusive) - **Physical properties**: coarse-grained, hard, massive; colour pink, grey or white with quartz, feldspar and mica; specific gravity 2.6-2.8; vitreous lustre. - **Engineering properties**: compressive strength 100-250 MPa; porosity less than 1%; low water absorption; very durable; takes a good polish; may have joints and sheet jointing; feldspar weathers to clay. - **Uses**: foundations for dams and bridges, building and monument stone, paving blocks, curbstones, aggregate, railway ballast, decorative slabs. #### Phyllite (metamorphic, foliated) - **Physical properties**: fine-grained, grey, green or black; silky sheen from fine mica; wavy foliation; hardness 3-4; specific gravity 2.7-2.9. - **Engineering properties**: compressive strength low to moderate (20-60 MPa), strongly anisotropic; splits along foliation; weathers easily; weak in slopes and tunnels, and often prone to landslides in the Lesser Himalaya (Nepal). - **Uses**: limited; roofing and flooring slabs where thick and hard; fill or road sub-base; generally unsuitable as aggregate or for heavy foundations. #### Limestone (sedimentary, chemical/organic) - **Physical properties**: fine- to coarse-grained, white, grey or yellowish; hardness 3; effervesces with dilute HCl; specific gravity 2.5-2.8. - **Engineering properties**: compressive strength 30-150 MPa; soluble in acidic water, so it forms caves and cavities (karst), leading to leakage at reservoirs and settlement of foundations. - **Uses**: raw material for cement and lime, aggregate, building stone, flux in metallurgy, flooring, road metal. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which set of properties matches granite? A. Compressive strength 20-60 MPa, strongly anisotropic B. Soluble in acidic water, forms cavities C. Fissile, slakes and swells D. Compressive strength 100-250 MPa, porosity under 1%, very durable Answer: D. Granite is strong, dense and durable. (Key point: Granite properties) 2. Why is phyllite weak in slopes and tunnels? A. It splits along foliation and weathers easily B. It dissolves into karst cavities C. It is highly porous like pumice D. It is massive and jointed like granite Answer: A. Strong anisotropy and foliation make it prone to landslides in the Lesser Himalaya. (Key point: Phyllite behaviour) 3. What problem is associated with limestone at reservoirs? A. Columnar jointing causes leakage B. Solution cavities (karst) cause leakage and foundation settlement C. Swelling of mica causes squeezing D. Foliation causes slope failure Answer: B. Limestone dissolves in acidic water, forming caves and cavities. (Key point: Limestone hazard) 4. Which is a main use of limestone? A. Roofing slabs B. Heavy dam foundations C. Raw material for cement and lime D. Railway sleepers Answer: C. Limestone is the raw material for cement and lime, besides aggregate and building stone. 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