The state that has the largest reserves of thorium in the form of monazite sands (beach sands) is

1. Thorium occurs in the mineral monazite, found in beach sands. 2. Kerala's coastal sands (especially at Kanyakumari and along Malabar coast) are rich in monazite. 3. Tamil Nadu and Odisha also have some monazite deposits. 4. Thorium is a key element for India's Stage-3 nuclear power programme. _Source: syllabus Social Science (Geography), Ch 5 "Minerals and Energy Resources", §5.3_