In inorganic chemistry and mineral resources, monazite sand is an important ore of which element?

Introduction / Context:
Monazite is a phosphate mineral that occurs in beach sands, especially along certain coastal regions. It is well known in general knowledge and chemistry examinations as an important source of certain radioactive and rare earth elements. One of the most famous elements obtained from monazite sand is thorium, which has been considered for use as nuclear fuel. This question asks you to recall which element is primarily associated with monazite as its ore.

Given Data / Assumptions:
- The mineral in question is monazite, often found in beach sands. - The options include thorium, manganese, aluminium, and copper. - We assume a standard general knowledge context about Indian and global mineral resources.

Concept / Approach:
Monazite is a complex phosphate that contains rare earth metals and thorium. In many general knowledge sources, it is specifically described as an ore of thorium. India, for example, has large deposits of monazite sands along its coasts, and these sands are cited as important for thorium resources. The other listed elements, such as manganese, aluminium, and copper, have their own common ores like pyrolusite, bauxite, and chalcopyrite, not monazite. Therefore, the correct association is between monazite and thorium.

Step-by-Step Solution:
Step 1: Recall the standard textbook statement that monazite sand is a chief source of thorium. Step 2: Connect monazite with discussions on nuclear fuels and India thorium reserves often mentioned in GK materials. Step 3: Recognise that manganese is usually obtained from ores such as pyrolusite and not from monazite. Step 4: Recognise that aluminium is mainly extracted from bauxite, and copper from ores like chalcopyrite or malachite. Step 5: Conclude that thorium is the element for which monazite is an important ore.

Verification / Alternative check:
You can confirm this by looking at any standard chemistry or geography textbook. In sections on minerals, monazite sand is repeatedly mentioned as an ore rich in thorium and some rare earths. Discussions on future nuclear energy strategies for countries with large monazite deposits also emphasise thorium. None of these references associate monazite primarily with manganese, aluminium, or copper, reinforcing that thorium is the correct answer.

Why Other Options Are Wrong:
Option B (Manganese) is wrong because manganese ores include pyrolusite MnO2 and others, not monazite. Option C (Aluminium) is incorrect since aluminium is mainly extracted from bauxite, a hydrated aluminium oxide, not from monazite. Option D (Copper) is incorrect because copper is commonly obtained from ores such as chalcopyrite CuFeS2, malachite, and cuprite, rather than monazite.

Common Pitfalls:
A frequent mistake is to confuse monazite with other mineral names and to guess based on incomplete memory. Some learners also mix up the ores of aluminium and thorium because both are discussed in the context of important national resources. To avoid confusion, remember the key association: bauxite with aluminium and monazite with thorium. Linking each ore to one standout element is a useful exam strategy.

Final Answer:
The correct answer is: Thorium.