Question

which statement is best supported by mohs hardness scale?

a piece of glass can be scratched by quartz, but not by calcite.

a fingernail will scratch quartz, but not calcite.

a piece of glass can be scratched by calcite, but not by quartz

a fingernail will scratch calcite, but not quartz.

Explanation:

Step1: Recall Mohs Hardness Scale principle

A mineral with a higher hardness number can scratch a mineral (or object) with a lower hardness number.

Step2: Analyze each option

• Option A:

Glass has a hardness of 5.5. Quartz has a hardness of 7 (can scratch glass). Calcite has a hardness of 3 (cannot scratch glass). So this option is incorrect.

• Option B:

Fingernail has a hardness of 2.5. Quartz has a hardness of 7 (fingernail cannot scratch quartz). Calcite has a hardness of 3 (fingernail cannot scratch calcite). So this option is incorrect.

• Option C:

Glass has a hardness of 5.5. Calcite has a hardness of 3 (cannot scratch glass). Quartz has a hardness of 7 (can scratch glass). So this option is incorrect.

• Option D:

Fingernail has a hardness of 2.5. Calcite has a hardness of 3 (fingernail cannot scratch calcite). Quartz has a hardness of 7 (fingernail cannot scratch quartz). Wait, no! Wait, Mohs scale: Fingernail (2.5) can't scratch Calcite (3) but also can't scratch Quartz (7). Wait, no - wait, actually, Mohs scale - a harder mineral (higher number) scratches a softer one. Fingernail (2.5) can't scratch Calcite (3) (since 2.5 < 3), but also can't scratch Quartz (7) (2.5 < 7). Wait, no - wait the option D: "A fingernail will scratch calcite, but not quartz" - no, 2.5 < 3 (so can't scratch calcite). Wait no - wait, hold on, let's re - check.
Wait, Mohs scale:

• Fingernail: 2.5
• Calcite: 3
• Quartz:7

A mineral (or object) can scratch another if its hardness is greater.
So a fingernail (2.5) cannot scratch calcite (3) (since 2.5 < 3) and cannot scratch quartz (7) (2.5 < 7). But wait, maybe there was a mis - read.
Wait, let's check again:

• Glass (5.5):
• Quartz (7) > 5.5 (can scratch glass)
• Calcite (3) < 5.5 (can't scratch glass)
• Fingernail (2.5):
• Calcite (3) > 2.5 (fingernail can't scratch calcite)
• Quartz (7) > 2.5 (fingernail can't scratch quartz)

But wait, the options:
Option D: "A fingernail will scratch calcite, but not quartz" - incorrect.
Wait, no - wait, hold on, maybe a typo in the problem. Wait, no - let's check the Mohs scale again.
Wait, the common objects:

• Fingernail: 2.5
• Copper Penny: 3.5
• Knife/Glass Plate:5.5
• Steel Nail:6.5
• Masonry Drill Bit:8.5

Minerals:

• Talc:1
• Gypsum:2
• Calcite:3
• Fluorite:4
• Apatite:5
• Orthoclase:6
• Quartz:7
• Topaz:8
• Corundum:9
• Diamond:10

So, a fingernail (2.5) can't scratch calcite (3) (since 2.5 < 3). But let's check the options again.
Wait, the first option: "A piece of glass can be scratched by quartz, but not by calcite" - glass (5.5), quartz (7) (7 > 5.5 - can scratch), calcite (3) (3 < 5.5 - can't scratch). So this option is correct.

Answer:

A. A piece of glass can be scratched by quartz, but not by calcite.