Question

graded quiz: basics of earth science
mohs hardness scale
mineral name scale number common object
diamond 10
corundum 9
topaz 8 masonry drill bit (8.5)
quartz 7
orthoclase 6 steel nail (6.5)
apatite 5 knife/glass plate (5.5)
fluorite 4
calcite 3 copper penny (3.5)
gypsum 2 fingernail (2.5)
talc 1
a geologist determines that a sample of a mineral cant 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) corundum.
b) orthoclase.
c) apatite.
d) fluorite.

Explanation:

Step1: Identify hardness of objects

A steel nail has a hardness of 6.5 and a masonry drill - bit has a hardness of 8.5 on the Mohs hardness scale. The mineral can't be scratched by a steel nail (so its hardness is > 6.5) and can be scratched by a masonry drill - bit (so its hardness is < 8.5).

Step2: Compare with mineral hardness values

Corundum has a hardness of 9, orthoclase has a hardness of 6, apatite has a hardness of 5, and fluorite has a hardness of 4. Since the mineral's hardness is between 6.5 and 8.5, it must be softer than corundum.

Answer:

A. corundum