That's correct. The basic difference between brine and hard rock is that brine is simple to purify but can't be extracted any faster than lithium salts dissolv

That's correct. The basic difference between brine and hard rock is that brine is simple to purify but can't be extracted any faster than lithium salts dissolve into water. Benefication and purification of hard rock lithium requires big grinders, flotation and acid baths, essentially the same process as mining any other metal. To justify building all that you need to be able to sell a lot, but once you do the cost is totally amortized. As an extreme example, coal mining in the US is so efficient that each miner produces 55 tons of coal per day. That kind of efficiency is enabled by the scale and investment. Current lithium sources are "easy pickings" and low-startup. It's like a single guy panning for gold by hand. He's just doing it for the chance at a buck, where gold is very convenient. Spodumene mining is froth flotation.