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

# Short note: Slate

Engineering Geology I · Chapter 4: Petrology

- Asked in: 2068 Chaitra, 1 marks
- Video: [GEOLOGY. Basalt. Marble. Slate.](https://www.youtube.com/watch?v=2yL79Lwg1NY) — Dorota GRZESIAK
- 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-slate
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-4

## Question

Write a short note on slate.

## Short answer

Slate is a fine-grained low-grade metamorphic rock from shale or clay, with slaty cleavage allowing it to split into thin strong sheets. Composed of mica, chlorite, quartz; durable, low porosity. Used for roofing, flooring; weak along cleavage, causing slope and tunnel issues.

## Answer

**Slate** is a fine grained, low-grade metamorphic rock formed from shale or clay by regional metamorphism. Its main feature is **slaty cleavage**, which allows it to split into thin, strong, smooth sheets. Colours are grey, black, green or purple. Minerals are mica (sericite), chlorite and quartz. It has low porosity and water absorption and is durable. Uses: roofing sheets, flooring, paving, damp-proof course and blackboards. In engineering it is weak along cleavage, which causes slope and tunnel problems.

## Check yourself

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

1. From which rock is slate formed?
   A. Limestone
   B. Shale or clay by regional metamorphism
   C. Sandstone
   D. Granite
   Answer: B. Slate is a low-grade metamorphic rock. (Key point: Slate origin)

2. What does slaty cleavage allow?
   A. Dissolving in water
   B. Large crystals to grow
   C. Splitting into thin, strong, smooth sheets
   D. Unbedded massive blocks
   Answer: C. This makes slate useful for roofing. (Key point: Slaty cleavage)

3. What is the engineering problem with slate?
   A. It is very porous
   B. It reacts with acid
   C. It swells like clay
   D. It is weak along cleavage, causing slope and tunnel problems
   Answer: D. Cleavage planes are weakness planes. (Key point: Engineering weakness)