Clearly Vale would consider Cliffs a competitor for Iron Ore products...that's why Vale may be interested in buying Cliffs.

My understanding is that Cliffs markets are mainly in North America. So who else supplies North America? I believe Rio Tinto bought the Iron Ore Company of Canada (IOC) formerly in Schefferville Quebec but now in Labrador City. Processing and shipping is done at Sept-Iles Quebec.

Other producing companies in Canada include Quebec Cartier Mining Co (QCM) and Wabush Mines.(Wabush is a Cliffs Mine)

The largest mining companies are BHP Billiton, Vale, Xstrata and Rio Tinto. I believe they all are suppliers of Iron Ore to some extent and Vale is the largest supplier.

The Chineese buy a lot of Iron Ore from mines in Australia including BHP Billiton. I did some contract work at Mount Newman mine in Northern Australia at Port Hedland but that was some time ago..

Mt Newman mine at Port Hedland is in the Pilbera region and I believe it is now owned by BHP.

FROM CLIFFS WEBSITE:

North America is currently the core of Cliffs’ business. Pellets from our operations are consumed by nearly all North American integrated steel producers, and virtually 100 percent of our current annual North American pellet capacity is committed under long-term contracts.

As the nation’s largest supplier of iron ore pellets to the integrated steel industry, we have the capacity to produce 38.1 million tons of pellets annually. Based on its percentage ownership of the mines it operates, Cliffs’ share of rated capacity is currently an estimated 25.5 million tons annually, representing approximately 31 percent of total North American annual pellet capacity.

Michigan

Empire Mine
Tilden Mine

Minnesota

Hibbing Taconite
Northshore Mining
United Taconite

Canada

Wabush Mine