Question

A geologist determines that a sample of a mineral can't be scratched by a steel nail but can be scratched by a masonry drill bit. Based on this information, the sample mineral has to be softer than A. orthoclase. B. fluorite. C. apatite. D. corundum.

Answer 1

Answer:

D. corundum.

Explanation:

Corundum is the hardest mineral in nature after diamond. For this reason it can only be scratched and worked by it. Mohs' hardness scale proves that corundum is indeed a very hard mineral and almost impossible to scratch. This scale states that the corundum has a hardness of 9.0, which indicates that it cannot be scratched by a drill.

Using the same scale, we can find out the hardness of the mineral exposed in the question. The mineral can be scratched by a drill, which means it has a hardness lower than 8.5, and the mineral cannot be scratched by a nail, which indicates that it has a hardness greater than 6.5. Based on this data, we can guarantee that this meniral is softer than the corundum.

Answer 2

D. Corundum

The mineral has a hardness greater than 6.5 (steel nail) and less than 8.5 (drill bit). All other choices have a hardness less than 8.5 but corundum has a hardness of 9.0. *Mohs hardness scale