Thorium is literally everywhere. You’ll find it in common dirt, granite, and conventional mines of all sorts (iron, aluminum, copper). The best source are heavy rare earths. Whenever you have heavy rare earths, you’ll always find Thorium...that’s just how the planet was made.
Thorium fuels the planet’s core with long term heart (along with Uranium). According to one mining CEO, a typical rare Earth mine can supply (considered a byproduct of normal operations) about 5000 tons of Thorium per year. If the Earth was on a thorium energy standard, that 5000 tons can supply the entire planet’s energy needs.
...and that’s just one mine.
Therefore, thorium is downright cheap to acquire, doesn’t need to be enriched like Uranium, and once separated can go strait into a LFTR reactor.
Thorium is non water soluble and can’t be metabolized. It’s also “fertile” as opposed to “fissile. By itself it can’t cause a chain reaction or produce heat until it’s bombarded by neutrons.
It is everywhere but not everywhere in economic concentrations.