---
title: "Define mineral"
subject: "Engineering Geology I"
chapter: 3
key: "semester_3/engineering_geology_i:define-mineral"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/define-mineral
site: BCT Engineering
---

# Define mineral

Engineering Geology I · Chapter 3: Crystallography & Mineralogy

- Asked in: 2066 Jestha (old course), 2 marks; 2065 Shrawan (old course), 1 marks; 2063 Baisakh (old course), 2 marks; 2059 Chaitra (old course), 1 marks (asked 4 times)
- Video: [Understanding Minerals](https://www.youtube.com/watch?v=8a7p1NFn64s) — Mike Sammartano
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/define-mineral
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-3

## Question

Define minerals (rock-forming minerals).

## Short answer

A mineral is a naturally occurring, inorganic, homogeneous solid with a definite chemical composition and ordered atomic structure, formed by geological processes. Rock-forming minerals are the few groups—dominantly silicates like quartz and feldspars—that constitute most crustal rocks, with silicates making up about 90%.

## Answer

A **mineral** is a naturally occurring, inorganic, homogeneous solid with a definite chemical composition (or a narrow range) and a regular internal atomic structure, usually formed by geological processes. Example: quartz (SiO₂), calcite (CaCO₃).

**Rock-forming minerals** are the few mineral groups that make up most of the rocks of the Earth's crust, about 20-30 in number. The main ones are:
- Silicates: quartz, feldspars, micas, amphiboles, pyroxenes, olivine.
- Carbonates: calcite, dolomite.
- Others: clay minerals, gypsum, oxides.

Silicates alone make up about 90% of the crust.

## Check yourself

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

1. A mineral is a:
   A. Naturally occurring, inorganic, homogeneous solid with definite composition and regular atomic structure
   B. Man-made organic solid
   C. Mixture of several rocks
   D. Liquid of fixed composition
   Answer: A. Natural, inorganic, solid, definite composition, ordered structure. (Key point: Definition)

2. Rock-forming minerals are:
   A. Rare minerals of economic value only
   B. The few (about 20-30) mineral groups that make up most of the crust's rocks
   C. All minerals known
   D. Minerals formed only in veins
   Answer: B. They are the abundant minerals forming the bulk of rocks. (Key point: Rock-forming minerals)

3. About what share of the crust is made of silicates?
   A. About 10%
   B. About 50% exactly by carbonates
   C. About 90%
   D. About 30%
   Answer: C. Silicates are the largest group, about 90% of the crust. (Key point: Silicates)

## Related in Engineering Geology I

- [Engineering significance of rock-forming minerals](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aengineering-significance-of-rockforming-minerals) — Engineering Geology I, chapter 3, asked 3×
- [Symmetry elements, crystal systems, rock-forming minerals](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Asymmetry-elements-crystal-systems-rockforming) — Engineering Geology I, chapter 3

## Related in other subjects

- [Rock forming minerals and significance](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Arock-forming-minerals) — Engineering Geology II, chapter 1, asked 6×