---
title: "Strike versus streak"
subject: "Engineering Geology I"
chapter: 3
key: "semester_3/engineering_geology_i:strike-versus-streak"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/strike-versus-streak
site: BCT Engineering
---

# Strike versus streak

Engineering Geology I · Chapter 3: Crystallography & Mineralogy

- Asked in: 2066 Bhadra (old course), 2 marks; 2066 Jestha (old course), 4 marks (asked 2 times)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/strike-versus-streak
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-3

## Question

Differentiate between strike and streak.

## Short answer

Strike is the compass direction of a horizontal line on an inclined bed, used in structural mapping. Streak is the colour of a mineral's powder obtained by rubbing it on a streak plate, used for mineral identification.

## Answer

These two terms belong to different fields: structural geology and mineralogy.

| Basis | Strike | Streak |
|---|---|---|
| Branch | Structural geology | Mineralogy |
| Meaning | Direction of the horizontal line on an inclined bed or plane | Colour of the powder of a mineral |
| Defined by | Intersection of the bed with a horizontal plane | Rubbing mineral on unglazed porcelain |
| Measured as | Compass bearing (azimuth) of the line, e.g. N 40° E | Colour name, e.g. red-brown |
| Instrument | Clinometer compass | Streak plate |
| Related term | Dip (at right angles to strike) | Colour (may differ from streak) |
| Use | Mapping, slope and tunnel stability | Mineral identification |
| Example | Bed striking N 30° W, dipping 40° NE | Hematite: red-brown streak; pyrite: greenish-black |

The strike of a bed is always at 90° to its true dip direction. Streak is more reliable than the colour of a mineral because it stays constant.

## Check yourself

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

1. Strike is:
   A. The colour of the powder of a mineral
   B. The angle of inclination of a bed
   C. The direction of the horizontal line on an inclined bed
   D. The direction of maximum slope
   Answer: C. Strike is the bed's intersection with a horizontal plane. (Key point: Strike)

2. Streak is:
   A. The bearing of a bed
   B. The shine of a mineral
   C. The bedding thickness
   D. The colour of the powder of a mineral on unglazed porcelain
   Answer: D. Streak belongs to mineralogy. (Key point: Streak)

3. How is strike related to true dip direction?
   A. They are at 90 degrees
   B. They are parallel
   C. They are at 45 degrees
   D. They are at 180 degrees
   Answer: A. Dip is measured at right angles to strike. (Key point: Dip relation)

4. Which instruments measure strike and streak respectively?
   A. Streak plate; clinometer compass
   B. Clinometer compass; streak plate
   C. Seismograph; hammer
   D. Hand lens; clinometer compass
   Answer: B. Strike by compass bearing, streak by rubbing on a porcelain plate. (Key point: Instruments)

## Related in Engineering Geology I

- [Colour versus streak of mineral](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Acolour-versus-streak-of-mineral) — Engineering Geology I, chapter 3
- [Primary and secondary structures; strike and dip](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aprimary-and-secondary-structures-strike) — Engineering Geology I, chapter 5, asked 2×