This means it can scratch glass (hardness 5.5) but cannot scratch quartz (hardness 7).

Here's a breakdown of Mohs hardness scale and what it means for basalt:

* Hardness 1: Talc - Can be scratched by your fingernail

* Hardness 2: Gypsum - Can be scratched by a fingernail

* Hardness 3: Calcite - Can be scratched by a copper coin

* Hardness 4: Fluorite - Can be scratched by a steel knife

* Hardness 5: Apatite - Can be scratched by a steel knife, but with more effort

* Hardness 6: Orthoclase - Can scratch glass

* Hardness 7: Quartz - Can scratch steel

* Hardness 8: Topaz - Can be scratched by a diamond

* Hardness 9: Corundum - Can only be scratched by a diamond

* Hardness 10: Diamond - The hardest known natural mineral

So, basalt is a fairly hard rock, but it can still be scratched by materials harder than it.