Suppliers have lots of power in most industries, and the mineral industry is no exception. To make a mine work, you need a few key resources beyond an ore body, and to get these you will need to work with suppliers. You need the logistical ability to get the ore to market, the power/energy to process the ore from its in situ state to a marketable state, the equipment to do the mining and the processing, the human capital, and the governmentally supplied right to operate.
Logistics, as everyone knows, can make or break any project. There is a point where the cost of the rail line or the slurry line outweighs the value of the product. For example, the cost of trucking from a gravel operation rapidly makes gravel only make sense as a local product. It used to be that more than 60 miles from the quarry to the customer for most markets was not economical for the product. Iron ore bodies require rail lines, and at times the suppliers of those lines—like in India and South Africa—have significant pricing power over the mining companies. Expansions and/or operating costs can and have been dictated by rail lines not owned by the mining companies. This is one of the reasons why iron ore companies so fiercely defend their own rail lines and the right to operate without interruption.
Energy is now a big issue, but what is interesting is that it is a cyclical issue. In Africa power is a big deal for mining companies (see my post from a couple weeks ago). The ability to get energy or electricity can significantly impact the value of a mine. The ideal state for mining companies is having long-term fixed price contracts for electricity or fuel, but that rarely happens unless you are in a downstream marketing situation like processing direct-reduced iron, aluminum, or alumina from bauxite.
Equipment is a cyclical issue that can represent a barrier to entry in the short term, but I have never seen a long-term economical project killed for lack of a tire or a truck. It is not like Komatsu or Caterpillar has the key truck for moving tonnes of iron ore and you can only use that one brand. Most mining equipment has low long-term switching costs. That is not to say that there are not large short-term market issues with equipment, but in the long term this is not a force that really scares me.
Human capital is hard to understand the value of. When you are undermanned and prices are high, that last guy is worth a lot of money. When prices are low and you are overstaffed, that last guy is hard to get rid of. I guess labor relations always matter in this business, and if you cannot get a guy to do work that needs to be done, it shuts you down. Again, though, this can be a long-term legacy issue if you are dealing with old line union operations, or a short-term boom-bust market issue. It, however, is not a barrier to entry, and the human capital really only has room to negotiate for higher prices when the market prices for the commodity goes up.
The government supplies the right to operate, and if you do not comply with the government of an area, they will shut you down. This supplier matters less if you are making sports shoes and you can set up shop one country over three weeks later. But ore bodies do not move, and so the government has lots of power as a supplier of permits and core laws. The counter issue, of course, is that governments want the tax revenues from businesses.
On the whole, the real structural barriers to entry are transportation and energy supply. These are the relatively fixed barriers and the suppliers of these things have the most long-term power. All the other supplier issues for this business can and will be solved as there are more suppliers in the long run than customers, and the cost to switch mining trucks or truck drivers is much lower than the cost of a bad contract. Of course unions and non-captive infrastructure that is core both will impact and the long-term profitability and success of any mine.