Good questions.

The players are equal shareholders (at least at the beginning) in a large cooperative that has one goal in 3 parts (as you correctly identified): mine the resource, refine it, and sell it. No CEO as I envision it, but you could say there's an "invisible hand" at play.

As for turns... good question. I see a turn as one mine/refine/sell cycle. But I'll admit I have not put as much thought into that.

Consider this though: say the market is moving in "real time" (condensed of course for the game). So if your processor is down, you can only sell refined inventory on hand. And just like in the real world, there would be natural consequences/costs for accumulation of inventory, so Just In Time processing is the key to success. So if you "miss a turn", you run the risk of irritating your customer, who in turn may devalue your product.

And just a thought: there could be hidden competitors, too, which adds another wrinkle dynamic. But that's another thought for later...