Underground Development

Defining a large underground resource

Initial underground resource estimate for Camino Rojo, extending down-plunge from the oxide open pit. 

• Measured and indicated: 3.95Moz Au, 4.16Moz AuEq​
  • 50.1Mt at 2.45 g/t Au and 2.58 g/t AuEq​​
• Inferred: 0.40Moz Au, 0.42Moz AuEq​
  • 5.6Mt at 2.21 g/t Au and 2.33 g/t AuEq

The Camino Rojo deposit comprises three continuous zones with distinct characteristics: 

1. The Camino Rojo Oxide Deposit (“Camino Rojo Oxides”), hosted by the Caracol formation,
2. The Camino Rojo Sulphide Deposit, the sulphide continuation of the Camino Rojo Oxides, also hosted by the Caracol formation (“Camino Rojo Sulphides” or “Sulphides”); and 
3. Zone 22, an extension of the Sulphides, hosted by the limestone-rich Indidura, Cuesta del Cura, La Peña, and Cupido formations.

Evolution of Camino Rojo Deposit:

Orla’s north-to-south drilling programs, spanning from 2020 to 2024, along with historical drilling, have been instrumental in enhancing the geological model. This work has significantly improved the understanding of the distribution and geometry of sulphide-bearing veins hosted within the Caracol Formation, which is the main host for both the Camino Rojo Oxides and Camino Rojo Sulphides 

Zone 22, an extension of the Sulphides, had been intersected in historical drilling but lacked a supporting geological model to define its geometry or extension into the deeper carbonate-rich formations below the Caracol Formation. Orla’s updated model enabled strategic drilling along a section drilled in 2023, targeting the deposit’s down-plunge extension. This drilling confirmed the model and supported further drilling in 2024 to define and expand Zone 22.

Initially, the development plan for the sulphide portion of the Camino Rojo deposit was conceived as a large open pit. However, initial estimates by previous operators, and later by Orla, indicated that such a scenario would require significant waste stripping, expanding the pit onto a third-party property, and constructing a substantial processing facility. An underground development scenario provides a more focused, high-value alternative by targeting higher-grade, metallurgically favourable parts of the deposit (those suitable for direct cyanide leaching) as an initial phase of mining. Subsequent phases would address mineralization requiring pre-treatment, such as pressure oxidation, prior to cyanidation. 

Additionally, underground development could operate in parallel with the ongoing oxide pit. The upcoming PEA (expected in 2026) is expected to evaluate the underground resource as an expansion of the current operation, enabling Orla to maximize the project’s full potential.

Underground Exploration

Orla is currently advancing a 20,000m drill program aimed at upgrading and expanding the Zone 22 resource, with 15,000 m drilled to date. Visual drill intercepts and assays continue to support the geological model and continuity of mineralization (Please see press release dated August 7, 2025). This program is expected to be completed by year end and is anticipated to extend and infill the down-plunge extension. 

The gold equivalent (AuEq) for heap leach material is calculated with the following formula: Au grade (g/t) + (US$0.84 x Ag recovery x Ag grade (g/t)) /(US$71.98 x Au recovery). The AuEq for CIL material is calculated with the following formula: Au grade (g/t) + (US$0.73 x Ag recovery x Ag grade (g/t)) / (US$68.34 x Au recovery). The AuEq for CIL w/POX material is calculated with the following formula: Au grade (g/t) + (US$0.73 x Ag recovery x Ag grade (g/t)) / (US$68.34 x Au recovery) + (US$0.00146 x Zn recovery x Zn grade (ppm)) / (US$68.34 x Au recovery).

Drill Results Tables

Future Plans

The next phase of exploration to support the possible development of the underground deposit (including Zone 22) includes the planning of an underground exploration drift (decline).  The exploration drift would allow access for closer-spaced drilling aimed at further resource definition and support technical studies to continue advancing toward a Mineral Reserve estimate. Permitting and early development planning [SS3] are underway, with construction of an exploration drift possibly starting as early as 2026.

Engineering and metallurgical studies are ongoing and will expand to deliver a Preliminary Economic Assessment (PEA) in 2026, providing a conceptual operating plan and highlight the potential value of developing underground operations.

Orla expects to continue with metallurgical testing and other technical work to support feasibility-level evaluations and final permitting for both underground operations and associated surface infrastructure. The conceptual development plan is designed to enable a smooth transition from open pit to underground mining at Camino Rojo.

Underground Mineral Resource Estimate

	Measured			Indicated			Measured & Indicated
Gold (Au)	kt	g/t	koz	kt	g/t	koz	kt	g/t	koz
Heap leach	7	1.95	0	1,704	2.9	159	1,711	2.9	159
CIL	–	–	–	12,475	2.07	832	12,475	2.07	832
FLOT/POX/CIL	–	–	–	35,900	2.56	2,958	35,900	2.56	2,958
Total – Gold	7	1.95	0	50,079	2.45	3,949	50,086	2.45	3,950
Silver (Ag)	kt	g/t	koz	kt	g/t	koz	kt	g/t	koz
Heap leach	7	31.5	7	1,704	13.2	722	1,711	13.3	729
CIL	–	–	–	12,475	8.7	3,480	12,475	8.7	3,480
FLOT/POX/CIL	–	–	–	35,900	11.1	12,847	35,900	11.1	12,847
Total – Silver	7	31.5	7	50,079	10.6	17,048	50,086	10.6	17,055
Zinc (Zn)	kt	%	Mlb	kt	%	Mlb	kt	%	Mlb
Heap leach	–	–	–	–	–	–	–	–	–
CIL	–	–	–	–	–	–	–	–	–
FLOT/POX/CIL	–	–	–	35,900	0.35	278	35,900	0.35	278
Total – Zinc	0	0	0	35,900	0.35	278	35,900	0.35	278
AUEQ (Au)	kt	g/t	koz	kt	g/t	koz	kt	g/t	koz
Heap leach	7	2.11	1	1,704	3.03	166	1,711	3.03	166
CIL	–	–	–	12,475	2.11	848	12,475	2.11	848
FLOT/POX/CIL	–	–	–	35,900	2.72	3,142	35,900	2.72	3,142
Total – AUEQ	7	2.11	1	50,079	2.58	4,156	50,086	2.58	4,156
Totals	kt	g/t	koz/Mlb	kt	g/t or %	koz/Mlb	kt	g/t or %	koz/Mlb
Au	7	1.95	0	50,079	2.45	3,949	50,086	2.45	3,950
Ag		31.5	7		10.6	17,048		10.6	17,055
Zn		–	–		0.25	278		0.25	278
AuEq		2.11	1		2.58	4,156		2.58	4,156

	Inferred
Gold (Au)	kt	g/t	koz
Heap leach	214	2.29	16
CIL	2,549	1.81	148
FLOT/POS/CIL	2,813	2.57	232
Total Au	5,576	2.21	396
Silver	kt	g/t	koz
Heap leach	214	15.1	104
CIL	2,549	10.2	835
FLOT/POS/CIL	2,813	11.2	1,010
Total Au	5,576	10.9	1,949
Zinc	kt	%	Mlb
Heap leach	–	–	–
CIL	–	–	–
FLOT/POS/CIL	2,813	0.42	26
Total Zn	2,813	0.42	26
AuEq	kt	g/t	koz
Heap leach	214	2.44	17
CIL	2,549	1.85	152
FLOT/POS/CIL	2,813	2.75	249
Total Zn	5,576	2.33	418
Totals	kt	g/t or %	koz/Mlb
Au	5,576	2.21	396
Ag		10.9	1,949
Zn		0.21	26
AuEq		2.33	418

Mineral Resources Notes:

1. CIM (2014) definitions were followed for Mineral Resources. The mineral resource estimate for Camino Rojo has an effective date of March 31, 2025.
2. The Qualified Person responsible for the mineral resource estimate is Marie-Christine Gosselin, P.Geo., Senior Resource Geologist of SLR Consulting (Canada) Ltd.
3. Mineral resources are estimated using a long-term price of US$2,300 /oz gold, US$1.25 /lb zinc and US$29 /oz silver and the following smelter terms: for oxide 99.9% payable Au and 98% payable Ag, and for sulphide 95% payable Au, 90% payable Ag and 95% payable Zn. Offsite costs (refining, transport and insurance) of US$145 /wmt transportation and US$230 /dmt treatment; a 2.5% NSR royalty.
4. Metallurgical recoveries vary according to geometallurgical domains from heap leach and flotation (CIL, CIL with POX) and are either constant or formula based. Heap leach recoveries range from 40% to 70% for gold and from 11% to 34% for silver. For CIL and CIL with POX, gold and silver recoveries are calculated using grade dependent formulae. The underground CIL mean recovery is 92% for gold and 36% for silver. The underground CIL with POX mean recovery is 85% for gold and 41% for silver. Zinc recovery by flotation is 80%. 
5. Mineral Resources are estimated in underground resource panels using NSR cut-off grades of 59.02 US$/t for leach material, 68.73 US$/t for CIL material, and 76.23 US$/t for CIL w/POX material. Underground resource panels have a minimum width of 2m.
6. The NSR for heap leach material is calculated with the following formula: NSR ($/t) = US$71.98 x Au recovery x Au grade + US$0.84 x Ag recovery x Ag grade (g/t). The NSR for flotation CIL material is calculated with the following formula: NSR ($/t) = US$68.34 x Au recovery x Au grade (g/t) + US$0.73 x Ag recovery x Ag grade (g/t). The NSR for CIL w/POX material is calculated with the following formula: NSR ($/t) = US$68.34 x Au recovery x Au grade (g/t) + US$0.73 x Ag recovery x Ag grade (g/T) + US$0.00146 x Zn recovery x Zn grade (ppm).
7. The gold equivalent (AuEq) for heap leach material is calculated with the following formula: Au grade (g/t) + (US$0.84 x Ag recovery x Ag grade (g/t)) /(US$71.98 x Au recovery). The AuEq for flotation CIL material is calculated with the following formula: Au grade (g/t) + (US$0.73 x Ag recovery x Ag grade (g/t)) / (US$68.34 x Au recovery). The AuEq for CIL w/POX material is calculated with the following formula: Au grade (g/t) + (US$0.73 x Ag recovery x Ag grade (g/t)) / (US$68.34 x Au recovery) + (US$0.00146 x Zn recovery x Zn grade (ppm)) / (US$68.34 x Au recovery).
8. Numbers may not add due to rounding.

The Mineral Resource estimate includes Inferred Mineral Resources that are considered too speculative geologically to have economic considerations applied to them that would enable them to be categorized as mineral reserves. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.

The following factors, among others, could affect the mineral resource estimate: commodity price and exchange rate assumptions, pit slope angles, assumptions used in generating the resource pit shell and underground resource panels, including metal recoveries, and mining and process cost assumptions. 

Underground Gallery