Lithium Mineral Resources and Ore Reserves

RNS Number : 2449K

Rio Tinto PLC

04 December 2025

Notice to ASX/LSE

Initial reporting of lithium Mineral Resources and Ore Reserves

4 December 2025

Rio Tinto today announces initial reporting of Mineral Resources and Ore Reserves[1] for seven lithium assets acquired as part of the purchase of Arcadium Lithium, namely:

· Four lithium brines deposits: the Fenix and Olaroz operations, and the Sal de Vida and Cauchari projects in Argentina

· Three hard rock spodumene deposits: the Whabouchi and Galaxy projects in Northern Quebec, and the Mt Cattlin operation in Western Australia

Mineral Resources are reported inclusive of Ore Reserves for lithium brines deposits[2], and in addition to Ore Reserves (exclusive) for hard rock spodumene deposits.

Fenix

Fenix is a lithium brines operation located in the Salar del Hombre Muerto in northwest Argentina. It is 100% owned by Rio Tinto and is currently in operation producing lithium carbonate.

Mineral Resources and Ore Reserves for the Fenix operation[3] are presented in Table A and Table B. Mineral Resources inclusive of Ore Reserves total 11.7 Mt Lithium Carbonate Equivalent (LCE) consisting of 2.7 Mt LCE of Measured Mineral Resources, 4.3 Mt LCE of Indicated Mineral Resources and 4.7 Mt LCE of Inferred Mineral Resources. Ore Reserves total 5.4 Mt LCE consisting of 1.2 Mt LCE Proven Ore Reserves and 4.1 Mt LCE Probable Ore Reserves³.

Olaroz

Olaroz is a lithium brines operation located in the Olaroz-Cauchari Salar, Jujuy, Argentina. It includes properties operated by Rio Tinto through its local subsidiary Sales de Jujuy, which is a joint venture between Rio Tinto (66.5%), Toyota Tsusho Corporation (25%) and Jujuy Energía y Minería Sociedad del Estado (JEMSE, 8.5%). In addition, Rio Tinto has 100% ownership of six properties to the north and west of the joint venture area which contain a portion of the reported Mineral Resources. All Ore Reserves are located within the Sales de Jujuy joint venture properties.

Mineral Resources and Ore Reserves for the Olaroz operation³ are presented in Table A and Table B. Mineral Resources inclusive of Ore Reserves total 19.7 Mt LCE consisting of 8.5 Mt LCE of Measured Mineral Resources, 8.4 Mt LCE of Indicated Mineral Resources and 2.8 Mt LCE of Inferred Mineral Resources. Ore Reserves total 2.7 Mt LCE consisting of 0.6 Mt LCE of Proven Ore Reserves and 2.2 Mt LCE Probable Ore Reserves.

Sal de Vida

Sal de Vida is a lithium brines project located in the Salar del Hombre Muerto, Catamarca, Argentina. It is 100% owned by Rio Tinto.

Mineral Resources and Ore Reserves for the Sal de Vida project³ are presented in Table A and Table B. Mineral Resources inclusive of Ore Reserves total 7.2 Mt LCE consisting of 3.5 Mt LCE of Measured Mineral Resources, 3.0 Mt LCE of Indicated Mineral Resources and 0.7 Mt LCE of Inferred Mineral Resources. Ore Reserves total 2.5 Mt LCE consisting of 0.4 Mt LCE of Proven Ore Reserves and 2.0 Mt LCE Probable Ore Reserves.

Cauchari

Cauchari is a lithium brines project located in the Olaroz-Cauchari Salar, Jujuy, Argentina. It is 100% owned by Rio Tinto.

Mineral Resources and Ore Reserves for the Cauchari project³ are presented in Table A and Table B. Mineral Resources inclusive of Ore Reserves total 6.0 Mt LCE consisting of 1.9 Mt LCE of Measured Mineral Resources, 2.6 Mt LCE of Indicated Mineral Resources and 1.5 Mt LCE of Inferred Mineral Resources. Ore Reserves total 1.1 Mt LCE consisting of 0.2 Mt LCE of Proven Ore Reserves and 0.9 Mt LCE Probable Ore Reserves.

Whabouchi

The Whabouchi project in northern Quebec, Canada, is a hard rock lithium-bearing spodumene deposit and is being developed by Nemaska Lithium, a joint venture between Investissement Québec (50%) and Rio Tinto (50%).

Mineral Resources and Ore Reserves for the Whabouchi project are presented in Table C and Table D. Mineral Resources exclusive of Ore Reserves total 26.9 Mt at 1.45% Li₂O, consisting of 18.7 Mt at 1.51% Li₂O of Indicated Mineral Resources and 8.3 Mt at 1.31% Li₂O of Inferred Mineral Resources[4]. Ore Reserves total 26.5 Mt at 1.32% Li₂O consisting of 10.5 Mt at 1.40% Li₂O of Proved Ore Reserves and 16.0 Mt at 1.27% Li₂O of Probable Ore Reserves[5].

Galaxy

The Galaxy project is a hard rock lithium-bearing spodumene deposit located in the northeastern part of the Superior Province in northern Quebec, Canada. It is 100% owned by Rio Tinto.

Mineral Resources and Ore Reserves for the Galaxy project are presented in Table C and Table D. Mineral Resources exclusive of Ore Reserves total 74.0 Mt at 1.25% Li₂O consisting of 18.1 Mt at 1.12% Li₂O of Indicated Mineral Resources and 55.9 Mt at 1.29% Li₂O of Inferred Mineral Resources[6]. Ore Reserves comprise 37.3 Mt at 1.27% Li₂O of Probable Ore Reserves[7].

Mt Cattlin

The Mt Cattlin operation is a lithium-bearing spodumene deposit in Western Australia. It is 100% owned by Rio Tinto. Mt Cattlin was placed on care and maintenance on 1 July 2025 due to market conditions. The potential for underground mining to extend the mine's life is the subject of current studies.

Mineral Resources and Ore Reserves for Mt Cattlin are presented in Table C and Table D. Mineral Resources exclusive of Ore Reserves total 11.3 Mt at 1.35% Li₂O, consisting of 0.1 Mt at 1.11% Li₂O of Measured Resources, 6.4 Mt at 1.42% Li₂O of Indicated Mineral Resources and 4.8 Mt at 1.27% Li₂O of Inferred Mineral Resources[8]. Ore Reserves total 2.3 Mt at 1.10% Li₂O consisting of 0.1 Mt at 0.80% Li₂O of Proved Ore Reserves and 2.2 Mt at 1.11% Li₂O of Probable Ore Reserves[9].

Table A Rio Tinto - Fenix, Olaroz, Sal de Vida and Cauchari Mineral Resources inclusive of Ore Reserves as at 30 June 2025

	Likely mining method⁽¹⁾	Measured Mineral Resources				Indicated Mineral Resources				Total Measured and Indicated Mineral
		as at 30 June 2025				as at 30 June 2025				Resources as at 30 June 2025
		Total Brine Volume	Average Lithium Grade	Lithium Metal	LCE	Total Brine Volume	Average Lithium Grade	Lithium Metal	LCE	Total Brine Volume	Average Lithium Grade	Lithium Metal	LCE
Lithium Brine^{(2) (3)}		Mm³	mg/l	Mt	Mt	Mm³	mg/l	Mt	Mt	Mm³	mg/l	Mt	Mt
Fenix (Argentina)⁽⁴⁾	B/E	810	630	0.5	2.7	1,040	780	0.8	4.3	1,840	710	1.3	7.0
Olaroz (Argentina)^{(4) (5)}	B/E	2,580	610	1.6	8.5	3,450	460	1.6	8.4	6,030	520	3.2	16.8
Sal de Vida (Argentina)⁽⁴⁾	B/E	880	750	0.7	3.5	760	740	0.6	3.0	1,640	750	1.2	6.5
Cauchari (Argentina)⁽⁴⁾	B/E	660	530	0.4	1.9	1,080	450	0.5	2.6	1,740	480	0.8	4.5

	Inferred Mineral Resources				Total Mineral Resources				Rio Tinto interest
	as at 30 June 2025				as at 30 June 2025				Rio Tinto interest
	Total Brine Volume	Average Lithium Grade	Lithium Metal	LCE	Total Brine Volume	Average Lithium Grade	Lithium Metal	LCE
Lithium Brine^{(2) (3)}	Mm³	mg/l	Mt	Mt	Mm³	mg/l	Mt	Mt	%
Fenix (Argentina)⁽⁴⁾	1,210	730	0.9	4.7	3,050	720	2.2	11.7	100.0
Olaroz (Argentina)^{(4) (5)}	1,490	360	0.5	2.8	7,520	490	3.7	19.7	73.5
Sal de Vida (Argentina)⁽⁴⁾	220	560	0.1	0.7	1,860	720	1.3	7.2	100.0
Cauchari (Argentina)⁽⁴⁾	590	470	0.3	1.5	2,330	480	1.1	6.0	100.0

Notes:

1. Type of Mine: B/E = brine extraction.

2. Lithium Brine Mineral Resources Ore Reserves are reported as in situ and inclusive of the Ore Reserves.

3. Lithium brine Resources lithium metal and LCE tonnages are in situ values assuming 100% recovery as per standard brine reporting practices. To obtain the equivalent tonnage for LCE, the estimated mass of lithium was multiplied by a factor that is based on the atomic weights of each element in lithium carbonate to obtain the final compound weight. The factor used was 5.323 to obtain LCE mass from lithium mass.

4. The estimates are based on: (1) specific yield values for hydrogeological units in the brine aquifer; (2) applicable lithium cut-off grade of 300 mg/l for Olaroz, Sal de Vida and Cauchari; (3) including only tenements controlled by Rio Tinto as of the effective date.

5. Olaroz Rio Tinto interest represents its fractional ownership in SDJ (66.5%), and 100% ownership in Olaroz Lithium, La Frontera, and Minera Andes on a mass-weighted basis.

Table B Rio Tinto - Fenix, Olaroz, Sal de Vida and Cauchari Ore Reserves as at 30 June 2025

	Type of mine⁽¹⁾	Proved Ore Reserves				Probable Ore Reserves				Total Ore Reserves
		as at 30 June 2025				as at 30 June 2025				as at 30 June 2025
		Anticipated Total Brine Volume	Average Lithium Grade	Lithium metal	LCE	Anticipated Total Brine Volume	Average Lithium Grade	Lithium metal	LCE	Anticipated Total Brine Volume	Average Lithium Grade	Lithium metal	LCE
Lithium Brine^{(2) (3)}		Mm³	Mg/L	Mt	Mt	Mm³	Mg/L	Mt	Mt	Mm³	Mg/L	Mt	Mt
Fenix (Argentina)⁽⁴⁾	B/E	320	730	0.2	1.2	1,260	620	0.8	4.1	1,570	640	1.0	5.4
Olaroz (Argentina)^{(4) (5)}	B/E	150	650	0.1	0.6	640	650	0.4	2.2	800	650	0.5	2.7
Sal de Vida (Argentina)⁽⁴⁾	B/E	100	800	0.1	0.4	510	740	0.4	2.0	620	760	0.5	2.5
Cauchari (Argentina)⁽⁴⁾	B/E	80	570	0.04	0.2	350	490	0.2	0.9	420	500	0.2	1.1

	Average Process Efficiency	Rio Tinto interest	Rio Tinto share recoverable metal	Rio Tinto share recoverable metal
	Average Process Efficiency	Rio Tinto interest	Lithium	LCE
Lithium Brine^{(2) (3)}	%	%	Mt	Mt
Fenix (Argentina)⁽⁴⁾	76.6	100.0	0.8	4.1
Olaroz (Argentina)^{(4) (5)}	60	66.5	0.2	1.1
Sal de Vida (Argentina)⁽⁴⁾	70	100.0	0.3	1.7
Cauchari (Argentina)⁽⁴⁾	60	100.0	0.1	0.7

Notes:

1. Type of Mine: B/E = brine extraction.

2. Anticipated total brine volume is the cumulative brine volume simulated from the entire wellfield over the life of mine whilst the extracted grade is averaged for the entire pumping period for the simulated wellfield. Lithium metal and LCE tonnages at each Reserve category are reported from a point of reference of the wellhead and assume 100% recovery. To obtain the equivalent tonnage for LCE, the estimated mass of lithium was multiplied by a factor that is based on the atomic weights of each element in lithium carbonate to obtain the final compound weight. The factor used was 5.323 to obtain LCE mass from lithium mass.

3. Rio Tinto share recoverable metal Lithium and LCE values apply the average process efficiency and the Rio Tinto % share.

4. Fenix, Olaroz, Sal de Vida and Cauchari Ore Reserves estimates are based on lithium cut-off grade of 400 mg/l, 410 mg/l, 470 mg/l and 350 mg/l respectively.

5. Olaroz Rio Tinto interest represents its fractional ownership in SDJ (66.5%). Ore Reserves are not produced from Rio Tinto's other ownership interests (Olaroz Lithium, La Frontera, or Minera Andes).

Table C Rio Tinto - Whabouchi, Galaxy and Mt Cattlin Mineral Resources exclusive of Ore Reserves as at 30 June 2025

	Likely mining method⁽¹⁾	Measured Mineral Resources as at 30 June 2025			Indicated Mineral Resources as at 30 June 2025			Total Measured and Indicated Mineral Resources as at 30 June 2025
		Measured Mineral Resources as at 30 June 2025			Indicated Mineral Resources as at 30 June 2025
		Tonnage	Grade		Tonnage	Grade		Tonnage	Grade
Lithium⁽²⁾		Mt	% Li₂O	ppm Ta₂O₅	Mt	% Li₂O	ppm Ta₂O₅	Mt	% Li₂O	ppm Ta₂O₅
Whabouchi (Canada)	O/P / UG	-	-		18.7	1.51	-	18.7	1.51	-
Galaxy (Canada)	O/P	-	-	-	18.1	1.12	-	18.1	1.12	-
Mt Cattlin (Australia)	O/P / UG	0.12	1.11	176	6.4	1.42	185	6.5	1.41	185

	Inferred Mineral Resources as at 30 June 2025			Total Mineral Resources as at 30 June 2025			Rio Tinto interest
	Inferred Mineral Resources as at 30 June 2025			Total Mineral Resources as at 30 June 2025			Rio Tinto interest
	Tonnage	Grade		Tonnage	Grade
Lithium⁽²⁾	Mt	% Li₂O	ppm Ta₂O₅	Mt	% Li₂O	ppm Ta₂O₅	%
Whabouchi (Canada)	8.3	1.31	-	26.9	1.45	-	50.0
Galaxy (Canada)	55.9	1.29	-	74.0	1.25	-	100.0
Mt Cattlin (Australia)	4.8	1.27	177	11.3	1.35	182	100.0

Notes:

1. Likely mining method: O/P = open pit/surface, U/G = underground.

2. Lithium Mineral Resources are stated as dry in situ tonnes.

Table D Rio Tinto - Whabouchi, Galaxy and Mt Cattlin Ore Reserves as at 30 June 2025

	Type of mine⁽¹⁾	Proved Ore Reserves as at 30 June 2025			Probable Ore Reserves as at 30 June 2025			Total Ore Reserves as at 30 June 2025			Average process efficiency		Rio Tinto interest	Rio Tinto share recoverable
		Proved Ore Reserves as at 30 June 2025			Probable Ore Reserves as at 30 June 2025			Total Ore Reserves as at 30 June 2025			Average process efficiency			Rio Tinto share recoverable
		Tonnage	Grade		Tonnage	Grade		Tonnage	Grade		Spodumene	Tantalite		Li₂O	Ta₂O₅
Lithium⁽²⁾		Mt	% Li₂O	ppm Ta₂O₅	Mt	% Li₂O	ppm Ta₂O₅	Mt	% Li₂O	ppm Ta₂O₅	%	%	%	Mt	Mlbs
Whabouchi (Canada)	O/P	10.5	1.40	-	16.0	1.27	-	26.5	1.32	-	85	-	50.0	0.15	-
Galaxy (Canada)	O/P	-	-	-	37.3	1.27	-	37.3	1.27	-	68.9	-	100.0	0.33	-
Mt Cattlin (Australia)
- Mt Cattlin Open pit	O/P	0.1	0.80	158	1.6	1.31	151	1.7	1.29	150	67	20	100.0	0.015	0.11
- Mt Cattlin Stockpiles	S/P	-	-	-	0.6	0.54	67	0.6	0.54	67	25	20	100.0	0.001	0.02
Mt Cattlin Total		0.1	0.80	158	2.2	1.11	129	2.3	1.10	130				0.015	0.13

Notes:

1. Type of Mine: O/P = open pit/surface, S/P = stockpile.

2. Lithium Ore Reserves are stated as dry mill feed tonnes.

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This announcement is authorised for release to the market by Andy Hodges, Rio Tinto's Group Company Secretary.

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[1] These Mineral Resources and Ore Reserves have been reported in accordance with the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves, 2012 (JORC Code) and the ASX Listing Rules in a release to the ASX dated 4 December 2025 titled "Initial reporting of lithium Mineral Resources and Ore Reserves: Table 1s" (Table 1 Release). Mineral Resources and Ore Reserves are quoted in this release on a 100 percent basis. The figures used to calculate Mineral Resources and Ore Reserves are often more precise than the rounded numbers shown in the tables, hence small differences may result if the calculations are repeated using the tabulated figures. Rio Tinto confirms that it is not aware of any new information or data that materially affects the information included in the Table 1 Release, that all material assumptions and technical parameters underpinning the estimates in the Table 1 Release continue to apply and have not materially changed, and that the form and context in which the Competent Persons' findings are presented have not been materially modified.

[2] For lithium brines deposits Lithium Metal and LCE Ore Reserves are reported at the well head and thus assume 100% recovery at that point. To obtain the equivalent tonnage for LCE, the estimated mass of lithium is multiplied by a factor that is based on the atomic weights of each element in lithium carbonate to obtain the final compound weight. The factor used was 5.323 to obtain LCE mass from lithium mass.

[3] The Competent Person responsible for the information in the Table 1 Release that relates to Fenix, Olaroz, Sal de Vida and Cauchari Mineral Resources and Ore Reserves is Sean Kosinski, who is a Certified Professional Geologist (CPG-12174) and a member of the American Institute of Professional Geologists.

[4] The Competent Person responsible for the information in the Table 1 Release that relates to Whabouchi Mineral Resources is Christian Beaulieu, who is a Member of the l'Ordre des géologues du Québec (license No. 101072).

[5] The Competent Person responsible for the information in the Table 1 Release that relates to Whabouchi Ore Reserves is Jeffrey Cassoff who is a Member of l'Ordre des Ingénieurs du Québec (license No. 5002252).

[6] The Competent Person responsible for the information in the Table 1 Release that relates to Galaxy Mineral Resources is Luke Evans, P.Eng., who is a Member of the l'Ordre des Ingénieurs du Québec (license No. 105567).

[7] The Competent Person responsible for the information in the Table 1 Release that relates to Galaxy Ore Reserves is Normand Lecuyer, P.Eng., who is a Member of l'Ordre des Ingénieurs du Québec (licence No. 34914).

[8] The Competent Person responsible for the information in the Table 1 Release that relates to Mt Cattlin Mineral Resources is Jamie Oppelaar, who is a Member of the Australasian Institute of Mining and Metallurgy.

[9] The Competent Person responsible for the information in the Table 1 Release that relates to Mt Cattlin Ore Reserves is based on information compiled under the supervision of Ali Sami who is a Fellow of the Australasian Institute of Mining and Metallurgy.

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END

UPDUSUVRVAUURRA

Date	4 Dec 2025
Time	07:01:01
Category	Corporate updates
ID	2449K

Date	4 Dec 2025
Time	07:01:01
Category	Corporate updates
ID	2449K

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Lithium Mineral Resources and Ore Reserves

Contacts

Media Relations,

United Kingdom

Media Relations,

Australia

Media Relations,

Canada

Media Relations,

US & Latin America

Investor Relations,

United Kingdom

Investor Relations,

Australia

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