Step 1: Understanding the Question: We are asked to correctly identify the mineral that occupies the number \(9\) spot on the Mohs scale of hardness.
Step 2: Key Concept: The Mohs scale of mineral hardness evaluates the scratch resistance of various minerals.
It ranges from \(1\) (the softest) to \(10\) (the hardest), based on the ability of a harder material to visibly scratch a softer one.
Step 3: Detailed Explanation:
Let's systematically review the upper end of the standard Mohs hardness scale:
Hardness \(7\) is assigned to Quartz.
Hardness \(8\) is assigned to Topaz.
Hardness \(9\) is assigned to Corundum, which chemically is aluminum oxide (\(Al_2O_3\)) and encompasses precious gemstones like ruby and sapphire.
Hardness \(10\) is assigned to Diamond, universally recognized as the hardest naturally occurring mineral on Earth.
Because the question specifically asks for the mineral representing a hardness value of \(9\), Corundum is the undeniable match.
Step 4: Final Answer: The correct mineral for hardness \(9\) is Corundum.