Conclusion
What might have gone wrong?
It was difficult to apply the same amount of pressure. Some of the rocks were very small while others were big. It may have affected where I scratched because the surface varied in size.
Was there an error in your work that you could fix for next time?
If a magnifying glass was used, scratch marks may have been identified.
How does your new learning fit with your background reading?
It was consistent with Mohs Hardness Scale.