To determine the hardness of the mineral based on the information that it can't be scratched by a steel nail but can be scratched by a masonry drill bit, we can refer to the Mohs scale of mineral hardness:
- Steel has a hardness of about 5.5 (it is usually able to scratch minerals that have a hardness of less than 5.5).
- Masonry drill bits typically are harder than steel and can scratch materials with hardness around 6 or higher.
Given this information:
- The mineral being scratched by the masonry drill bit indicates that it is softer than the bit (greater than 6).
- The mineral not being scratched by the steel nail indicates that its hardness is less than 5.5.
From the options given:
- A) Apatite (hardness 5)
- B) Orthoclase (hardness 6)
- C) Corundum (hardness 9)
- D) Fluorite (hardness 4)
Since the mineral can be scratched by the masonry drill bit (hardness >6) and cannot be scratched by a steel nail (hardness <5.5), then we need to consider the hardness of the available minerals:
- Apatite (5) is softer than the mineral
- Orthoclase (6) is about the same hardness as steel and cannot be scratched by it
- Corundum (9) is much harder than the mineral
- Fluorite (4) is also softer than the mineral
The only mineral that fits the criteria (softer than the masonry drill bit but harder than the steel nail) is Apatite (hardness 5).
Therefore, the answer is:
A) apatite.