I came across a passage from "Human Action" by Ludwig von Mises that I don't understand:
The production of one unit of the commodity m requires, besides the employment of various nonspecific factors, the employment of one unit of each of the two absolutely specific factors a and b. Neither a nor b can be replaced by any other factor; on the other hand a is of no use when not combined with b and vice versa. The available supply of a by far exceeds the available supply of b. It is therefore not possible for the owners of a to attain any price for a. The demand for a always lags behind the supply; a is not an economic good. If a is a mineral deposit the extraction of which requires the use of capital and labor, the ownership of the deposits does not yield a royalty. There is no mining rent.
He goes on to describe how a cartel can restrict the supply of a to slightly lower than the supply of b, and the owners of b can react in kind.
What I don't understand is why the free market can't restrict the supply of a on its own to match the supply of b, as is done in any normal pricing process. And what did Mises mean by
The available supply of a by far exceeds the available supply of b.
Does he mean the supply of a is larger than the supply of b at every price?
Can someone give a concrete example of how such a situation might go down step by step with concrete values for demand and supply of a and b?