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

# Short note: Lutite

Engineering Geology I · Chapter 4: Petrology

- Asked in: 2076 Asoj, 4 marks
- 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-lutite
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-4

## Question

Write a short note on lutite.

## Short answer

Lutite is a fine-grained clastic sedimentary rock composed of clay- and silt-size particles (<0.06 mm). It is soft, low strength, swells when wet, low permeability, and is a poor foundation rock but a good seal. Used for bricks, tiles; metamorphoses to slate, phyllite, schist.

## Answer

**Lutite** (argillaceous rock) is a fine-grained clastic sedimentary rock composed of clay- and silt-size particles (<0.06 mm). Lutites are formed by deposition of mud in quiet water (lakes, lagoons, deep sea) and later compaction.

- **Types**: clay, mudstone, siltstone, claystone and shale. Shale is the fissile variety.
- **Texture and structure**: very fine, pelitic; laminated or thinly bedded; may be fissile.
- **Minerals**: clay minerals (kaolinite, illite, montmorillonite), fine quartz and mica.
- **Properties**: soft, low strength, plastic when wet, absorbs water, swells and slakes, low permeability.
- **Engineering significance**: poor foundation rock, unstable in slopes and tunnels, weak when wet; however, being impermeable, it is a good seal for reservoirs and dam abutments. Used for bricks, tiles, pottery and cement.
- On metamorphism, lutite changes to slate, phyllite and schist.

## Check yourself

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

1. Lutite consists of what grain size?
   A. Pebbles above 2 mm
   B. Sand 0.06-2 mm
   C. Clay and silt (<0.06 mm)
   D. Interlocking crystals
   Answer: C. It is an argillaceous rock. (Key point: Lutite definition)

2. Where is lutite deposited?
   A. Fast rivers
   B. Volcanic vents
   C. Desert dunes
   D. Quiet water such as lakes, lagoons and deep sea
   Answer: D. Fine mud settles in still water. (Key point: Lutite formation)

3. Which engineering advantage does lutite have despite weakness?
   A. Being impermeable, it seals reservoirs and dam abutments
   B. High strength for foundations
   C. Excellent ballast
   D. Resistance to slaking
   Answer: A. Low permeability is useful. (Key point: Lutite engineering)

4. Sequence on metamorphism of lutite?
   A. Marble, quartzite, hornfels
   B. Slate, phyllite, schist
   C. Granite, gneiss
   D. Basalt, gabbro
   Answer: B. Increasing grade of metamorphism. (Key point: Lutite metamorphism)