Question

According to the Mohs Scale of Hardness, which mineral has a relative hardness value of 9?

• A. Quartz
• B. Diamond
• C. Corundum
• D. Topaz

Hint:

Remember the top three minerals in Mohs hardness scale: {Quartz (7) → Topaz (8) → Corundum (9) → Diamond (10)}. Diamond is the hardest natural mineral.

Answer 1

The Correct Option is C

Concept: The Mohs Scale of Hardness is a qualitative scale used to measure the resistance of a mineral to scratching. It was developed by the German mineralogist Friedrich Mohs in 1812. The scale ranges from 1 (softest) to 10 (hardest). The standard Mohs hardness scale is:

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

Step 1: Identify the mineral corresponding to hardness value 9.
From the Mohs hardness scale, the mineral with a hardness value of 9 is Corundum. Corundum is composed mainly of aluminum oxide (\(Al_2O_3\)) and includes gemstones such as ruby and sapphire.
Step 2: Eliminate other options.

• Quartz has hardness 7.
• Topaz has hardness 8.
• Diamond has hardness 10, the hardest natural mineral.

Thus, the mineral with a Mohs hardness of 9 is Corundum.