Step 1: Understanding the mineral.
Diaspore is an important ore of aluminum. It is a mineral form of aluminum oxide hydroxide (AlO(OH)). Other minerals like limonite, azurite, and chalcopyrite do not contain significant amounts of aluminum.
Step 2: Analyzing the options.
(A) Diaspore: Correct — This is an ore of aluminum.
(B) Limonite: This is an ore of iron, not aluminum.
(C) Azurite: This is a copper carbonate mineral, not an aluminum ore.
(D) Chalcopyrite: This is a copper iron sulfide mineral, not an aluminum ore.
Step 3: Conclusion.
The correct answer is (A) Diaspore, as it is a mineral of aluminum.