---
title: "Identify metamorphic rock; properties of sandstone and granite"
subject: "Engineering Geology I"
chapter: 4
key: "semester_3/engineering_geology_i:identify-metamorphic-rock-properties-of"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/identify-metamorphic-rock-properties-of
site: BCT Engineering
---

# Identify metamorphic rock; properties of sandstone and granite

Engineering Geology I · Chapter 4: Petrology

- Asked in: 2080 Baisakh, 4 marks
- Video: [Identifying Metamorphic Rocks -- Earth Rocks!](https://www.youtube.com/watch?v=HUydPhIaQQU) — Earth Rocks!
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/identify-metamorphic-rock-properties-of
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-4

## Question

How do you identify a metamorphic rock in the field? Describe the physical properties of sandstone and granite.

## Short answer

Metamorphic rocks show foliation, slaty cleavage, crystalline sugary texture, typical minerals (garnet, mica), and distorted structures. Sandstone: clastic, quartz grains, porous, strength 20–170 MPa depending on cement. Granite: coarse crystalline, quartz/feldspar, specific gravity2.6–2.8, strength100–250 MPa.

## Answer

#### Identifying a metamorphic rock in the field
1. **Foliation**: parallel alignment of minerals, banding or schistosity (slate, phyllite, schist, gneiss).
2. **Slaty cleavage**: splits into thin, hard slabs.
3. **Crystalline, sugary texture** (marble, quartzite), with no layers or fossils.
4. **Typical minerals**: garnet, kyanite, chlorite, mica, staurolite, talc.
5. **Distorted structures**: folds, crumpled bands, stretched pebbles.
6. Often hard, dense and found in mountain belts or near intrusions.

#### Physical properties of sandstone
- Sedimentary, clastic rock of sand-sized grains (mostly quartz) cemented by silica, calcite or iron oxide.
- Colour: white, yellow, red, brown or grey; bedded; granular texture, gritty feel.
- Specific gravity 2.2-2.7; porosity 5-25%; compressive strength 20-170 MPa depending on cement; hardness 6-7 for quartz grains.

#### Physical properties of granite
- Igneous, intrusive, coarse-grained, crystalline rock of quartz, feldspar and mica or hornblende.
- Colour: pink, grey or white, speckled; massive, hard; specific gravity 2.6-2.8; porosity under 1%; compressive strength 100-250 MPa; takes high polish.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which feature identifies metamorphic rocks?
   A. Fossils and cross-bedding
   B. Foliation or banding, with no fossils
   C. Vesicles
   D. Rounded pebbles
   Answer: B. Foliation, sugary texture and metamorphic minerals are the clues. (Key point: Foliation)

2. Sandstone is
   A. a foliated metamorphic rock
   B. an intrusive igneous rock
   C. a clastic sedimentary rock of sand-sized, mostly quartz grains cemented by silica, calcite or iron oxide
   D. a chemical rock of calcite crystals
   Answer: C. Sandstone is clastic sedimentary. (Key point: Sandstone)

3. Which comparison of porosity is right?
   A. Both under 1%
   B. Sandstone under 1%; granite 5-25%
   C. Both 5-25%
   D. Sandstone 5-25%; granite under 1%
   Answer: D. Granite is dense and crystalline. (Key point: Porosity contrast)

4. Which describes granite?
   A. Intrusive, coarse-grained, 100-250 MPa, takes high polish
   B. Bedded, gritty, 20-170 MPa depending on cement
   C. Foliated, silky, weak
   D. Glassy and vesicular
   Answer: A. The answer lists these for granite. (Key point: Granite properties)

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