---
title: "Why quartz is the most resistant mineral"
subject: "Engineering Geology I"
chapter: 3
key: "semester_3/engineering_geology_i:why-quartz-is-the-most"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/why-quartz-is-the-most
site: BCT Engineering
---

# Why quartz is the most resistant mineral

Engineering Geology I · Chapter 3: Crystallography & Mineralogy

- Asked in: 2064 Jestha (old course), 2 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/why-quartz-is-the-most
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-3

## Question

Mention two points to clarify why quartz is the most resistant mineral.

## Short answer

Quartz has a strong three-dimensional framework of Si-O covalent bonds, giving hardness 7 and high chemical stability. It has no cleavage, breaking with conchoidal fracture, so no planes of weakness exist for weathering, allowing it to persist as sand grains.

## Answer

1. **Strong chemical structure**: quartz is made of SiO₂ in a three-dimensional framework of strong Si-O covalent bonds, giving high hardness (7) and chemical stability; it hardly reacts with water or weak acids.
2. **No cleavage**: quartz breaks with a conchoidal fracture, with no planes of weakness along which weathering and disintegration can start. Hence it remains as sand grains when other minerals weather to clay.

## Check yourself

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

1. Why is quartz chemically stable and hard?
   A. Its SiO2 forms a 3D framework of strong Si-O covalent bonds
   B. It has layers of weak bonds
   C. It is made of calcium carbonate
   D. It has perfect cleavage
   Answer: A. Strong bonds give hardness 7 and stability. (Key point: Structure)

2. Why is the absence of cleavage important for quartz's resistance?
   A. Cleavage makes minerals stronger
   B. No planes of weakness along which weathering can start
   C. No cleavage makes it soluble
   D. It breaks into sheets
   Answer: B. It breaks conchoidally. (Key point: Cleavage)

3. When other minerals weather to clay, quartz:
   A. Turns into clay
   B. Dissolves
   C. Remains as sand grains
   D. Turns to calcite
   Answer: C. It resists weathering. (Key point: Weathering result)

## Related in Engineering Geology I

- [Engineering significance of marble](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aengineering-significance-of-marble) — Engineering Geology I, chapter 4

## Related in other subjects

- [Diffuse layer; most swelling mineral](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Adiffuse-layer-swelling-clay) — Soil Mechanics, chapter 4
- [Quartz significance for hydropower project](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aquartz-hydropower-significance) — Engineering Geology II, chapter 1
- [Principal points and image, two lenses](https://www.bctengineer.com/question.md?key=semester_1%2Fengineering_physics%3Atwo-lenses-principal-points-image) — Engineering Physics, chapter 5
- [Chemical and mineral admixtures; plasticizers](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aplasticizer-water-reduction) — Concrete Technology and Masonry Structure, chapter 1