---
title: "Short note: Shale"
subject: "Engineering Geology I"
chapter: 4
key: "semester_3/engineering_geology_i:short-note-shale"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/short-note-shale
site: BCT Engineering
---

# Short note: Shale

Engineering Geology I · Chapter 4: Petrology

- Asked in: 2068 Chaitra, 1 marks
- Video: [What Is Shale?](https://www.youtube.com/watch?v=Dy-t9K2Piww) — Geology Johnson
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/short-note-shale
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-4

## Question

Write a short note on shale.

## Short answer

Shale is a fine-grained fissile sedimentary rock formed by compaction of clay and silt. It contains clay minerals and quartz, is soft and weak, and swells and slakes on wetting, causing poor foundation and slope stability. Used in bricks and cement.

## Answer

**Shale** is a fine-grained clastic (argillaceous) sedimentary rock formed by compaction of clay and silt. It is thinly bedded and splits easily into thin layers along bedding planes (fissility). The main minerals are clay minerals (illite, kaolinite) with quartz. It is soft and weak, absorbs water, and swells and slakes on wetting and drying. Engineering problems: poor foundation and slope stability, and swelling in tunnels. It is used in brick and cement manufacture and metamorphoses to slate.

## Check yourself

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

1. What is fissility in shale?
   A. Dissolving in acid
   B. Splitting along cleavage after metamorphism
   C. Ability to split into thin layers along bedding planes
   D. Glassy fracture
   Answer: C. Shale is thinly bedded and splits easily. (Key point: Shale texture)

2. Which problem is typical of shale?
   A. Extreme hardness
   B. Wide solution cavities
   C. Columnar jointing
   D. Swelling and slaking on wetting and drying
   Answer: D. Clay minerals absorb water, swell and slake. (Key point: Shale problems)

3. Shale on metamorphism changes to what?
   A. Slate
   B. Marble
   C. Quartzite
   D. Gneiss directly
   Answer: A. Shale to slate is low-grade regional metamorphism. (Key point: Shale metamorphism)