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Definitions and exchange rates

Non Mining Definitions

Mining and technical definitions

Throughout this document, the collective expressions Rio Tinto, Rio Tinto Group and Group are used for convenience only. Depending on the context in which they are used, they mean Rio Tinto plc and/or Rio Tinto Limited and/or one or more of the individual companies in which Rio Tinto plc and/or Rio Tinto Limited directly or indirectly own investments, all of which are separate and distinct legal entities.

Unless the context indicates otherwise, the following terms have the meanings shown below:

Alumina	Aluminium oxide. It is extracted from bauxite in a chemical refining process and is subsequently the principal raw material in the electro-chemical process by which aluminium is produced.
Anode and cathode copper	At the final stage of the smelting of copper concentrates, the copper is cast into specially shaped slabs called anodes for subsequent refining to produce refined cathode copper.
Bauxite	Mainly hydrated aluminium oxides (AL₂O₃.2H₂O). Principal ore of alumina, the raw material from which aluminium is made.
Bioleaching	The deliberate use of bacteria to speed the chemical release of metals from ores.
Block caving	An underground bulk mining method. It involves undercutting the orebody to induce ore fracture and collapse by gravity. The broken ore is recovered through draw points below.
Borates	A generic term for mineral compounds which contain boron and oxygen.
Cathode copper	Refined copper produced by electrolytic refining of impure copper or by electro-winning.
Classification	Separating crushed and ground ore into portions of different size particles.
Coking coal	By virtue of its carbonisation properties, it is used in the manufacture of coke, which is used in the steel making process. Also known as metallurgical coal.
Concentrate	The product of a physical concentration process, such as flotation or gravity concentration, which involves separating ore minerals from unwanted waste rock. Concentrates require subsequent processing (such as smelting or leaching) to break down or dissolve the ore minerals and obtain the desired elements, usually metals.
Cutoff grade	The lowest grade of mineralised material considered economic to process. It is used in the calculation of the quantity of ore present in a given deposit.

Conversion of weights and measures

1 troy ounce = 31.1 grams
1 kilogram = 32.15 troy ounces
1 kilogram = 2.2046 pounds
1 metric tonne = 1,000 kilograms
1 metric tonne = 2,204.6 pounds
1 metric tonne = 1.1023 short tons
1 short ton = 2,000 pounds
1 long ton = 2,240 pounds
1 gram per metric tonne = 0.02917 troy ounces per short ton
1 gram per metric tonne = 0.03215 troy ounces per metric tonne
1 kilometre = 0.6214 miles

Exchange rates

The following tables show, for the periods and dates indicated, certain information regarding the exchange rates for the pound sterling and Australian dollar, based on the Noon Buying Rates for pounds sterling and Australian dollars expressed in US dollars per £1.00 and per A$1.00.

**Pounds sterling**
Year ended 31 December*	Period end	Average rate	High	Low
2008	1.44	1.86	2.03	1.44
2007	1.99	2.00	2.11	1.92
2006	1.96	1.84	1.98	1.72
2005	1.73	1.82	1.93	1.71
2004	1.93	1.83	1.95	1.76

*The Noon Buying Rate on such dates differed slightly from the rates used in the preparation of Rio Tinto's financial statements as of such date. No representation is made that pound sterling and Australian dollar amounts have been, could have been or could be converted into dollars at the Noon Buying Rate on such dates or at any other dates.

**Australian dollars**
Year ended 31 December*	Period end	Average rate	High	Low
2008	0.698	0.852	0.983	0.607
2007	0.878	0.839	0.937	0.772
2006	0.788	0.753	0.791	0.706
2005	0.734	0.763	0.799	0.727
2004	0.783	0.737	0.798	0.686