Question

mohs hardness scale mineral name scale number common object increasing hardness diamond 10 masonry drill bit (8.5) corundum 9 topaz 8 steel nail (6.5) quartz 7 orthoclase 6 knife/glass plate (5.5) apatite 5 fluorite 4 copper penny (3.5) calcite 3 fingernail (2.5) gypsum 2 talc 1 if an unknown mineral can scratch a penny but cannot scratch a steel nail, what is its approximate hardness? between 2.5 and 3.5 between 3.5 and 6.5 between 3.5 and 4.5 between 6.5 and 7.5

Explanation:

Step1: Identify penny's hardness

A copper penny has a hardness of 3.5 on the Mohs scale.

Step2: Identify steel - nail's hardness

A steel nail has a hardness of 6.5 on the Mohs scale.

Step3: Determine unknown mineral's hardness range

Since the unknown mineral can scratch a penny (hardness 3.5) but not a steel nail (hardness 6.5), its hardness is between 3.5 and 6.5.

Answer:

Between 3.5 and 6.5