FACTBOX - The world's biggest mining companies

(Reuters) - Chinese mining group Chinalco said on Friday it had teamed up with U.S. aluminium producer Alcoa (AA.N) to buy a 12 percent in Rio Tinto (RIO.L)(RIO.AX).

The move comes days ahead of a deadline for BHP Billiton (BLT.L)(BHP.AX), the world's biggest miner, to make a firm offer for Rio Tinto or to drop its proposed takeover, which Rio has so far resisted.

Chinalco and Alcoa said they did not currently intend to make an offer for Rio, but reserved the right to do so if Rio received a firm bid from a third party.

Below is a list of the top 10 mining firms in 2006, ranked according to their controlled share of the total value of global non-fuel minerals production, in percent. The list was compiled by industry analysts Raw Materials Group.

Company Country Share 2006

CVRD VALE.SA RIO.N Brazil 5.4

BHP Billiton (BLT.L) (BHP.AX) Australia 4.8

Anglo American (AAL.L) Britain 4.3

Rio Tinto (RIO.L) (RIO.AX) Britain 4.3