Thorium Ore Identification

This question asks to identify the ore of the radioactive element Thorium ($Th$) from the given options. Analyzing each option helps determine the correct mineral.

Mineral Ore Analysis

• Carnotite: This mineral is primarily known as an ore of Uranium ($U$) and Vanadium ($V$). Its chemical composition is typically represented as $K_2(UO_2)_2(VO_4)_2 \cdot 3H_2O$.
• Torbernite: Also known as chalcolite, this is a hydrated copper uranium phosphate mineral. It is recognized as an ore of Uranium ($U$). Its formula is $Cu(UO_2)_2(PO_4)_2 \cdot 12H_2O$.
• Monazite: This is a phosphate mineral belonging to the rare earth elements group. Crucially, Monazite is a major ore for Thorium ($Th$), often containing 3-10% Thorium by weight. It also contains rare earth elements like Cerium ($Ce$) and Lanthanum ($La$). Its general formula is $(Ce, La, Nd, Th)PO_4$.
• Pitchblende: This is the most abundant naturally occurring radioactive mineral on Earth. It is essentially a massive variety of the mineral Uraninite ($UO_2$). Pitchblende is the principal ore for Uranium ($U$) and also contains significant amounts of Thorium ($Th$), Vanadium ($V$), and other elements. While it contains Thorium, it's primarily classified as a Uranium ore, and Monazite is more specifically and commonly cited as a primary Thorium ore due to its consistent and high Thorium content.

Conclusion on Thorium Ore

Based on the analysis, Monazite is distinctively recognized as a primary ore of Thorium ($Th$) due to its significant and consistent concentration of this element.