THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION AS STIPULATED UNDER THE UK VERSION OF THE MARKET ABUSE REGULATION NO 596/2014 WHICH IS PART OF ENGLISH LAW BY VIRTUE OF THE EUROPEAN (WITHDRAWAL) ACT 2018, AS AMENDED.  ON PUBLICATION OF THIS ANNOUNCEMENT VIA A REGULATORY INFORMATION SERVICE, THIS INFORMATION IS CONSIDERED TO BE IN THE PUBLIC DOMAIN.

18 February 2025

Great Southern Copper plc

("GSC" or the "Company")

Diamond Drilling Programme Completed at Mostaza Mine, Cerro Negro Project

All holes intersect visible copper mineralisation. Planning for Phase II drilling commenced

Great Southern Copper plc (LSE: GSCU), the company focused on copper-gold-lithium exploration in Chile, is pleased to provide an update on its Phase I diamond drilling programme at the Cerro Negro project in northern Chile, where drilling at the historical Mostaza mine commenced on 5 January 2025¹.

Highlights:

·    Phase I drill programme completed with nine diamond holes drilled for 1,002.6 m

·    Drilling targeted high-grade, structurally-controlled high-sulphidation style Cu-Ag mineralisation with the aim to;

o  confirm historical drilling grades and widths beneath the Mostaza open pit (Lens 2),

o  test extensions of Lens 2 mineralisation to depth and along strike of historical drill intercepts, and

o  test beneath outcropping Lenses 3-4 mineralisation along trend to south of the mine

·    All holes intersected visual evidence of copper mineralisation comprising abundant disseminations, veins, crackle-vein networks and breccia-hosted chalcocite-bornite-chalcopyrite in zones up to 32.3m downhole width* (Figures 1 and 2)

·    Samples for all holes DD001 - 009 have been dispatched to ALS laboratories for assaying. Assay results for initial holes are anticipated in the coming weeks

·    Planning and permitting for the next phase of drilling is in progress. Work is likely to include metallurgical testing

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: "Our Phase I diamond drilling programme at the Mostaza copper-silver mine has been very successful and we are eager to receive our first assay results.

Planning and permitting is already underway for the second phase of drilling which is proposed to include further resource and exploration drilling plus metallurgical test-work. Geophysics surveys are also being considered to assist with exploration for buried extensions and repetitions of the high-grade mineralised lenses and for deeper porphyry type copper mineralisation.

We also anticipate results for the scout RC drilling programme at Viuda which targeted potential porphyry style mineralisation."

Diamond drill campaign at Cerro Negro

Phase I diamond drilling at the Mostaza Cu-Ag mine is now completed with nine holes drilled for a total of 1,002.6m. Drilling targeted high-grade, high sulphidation style Cu-Ag mineralisation hosted in structurally-controlled, anastamosing lodes or "lenses" with the aim to;

I.     Confirm historical grades and thicknesses of historical drilling (CNG25-DD001),

II.    Resource drill holes to test the extent of Lens 2 mineralisation at depth and along strike of historical drill intercepts (holes CNG25-002 - 005), and

III.   Exploration drill holes to test beneath outcropping Lens 3-4 mineralisation along trend to south of the mine (holes CNG25-006 - 009)

All holes intersected copper mineralisation and a summary of the visual mineralised intervals includes;

CNG25 DD001: 20m* of visible copper mineralisation from 27.00 to 47.00m

CNG25 DD002: 4.3m* of visible copper mineralisation from 38.90 to 43.20m (off-set by dyke)

CNG25 DD003: 18.8m* of visible copper mineralisation from 36.60 to 55.40m (thickening with depth)

CNG25 DD004: 3m* of visible copper mineralisation from 28.70 to 31.70m (off-set by dykes/faults)

CNG25 DD005: 23.5m* of visible copper mineralisation from 32.90 to 56.40m (thickening with depth)

CNG25 DD006: 8.6m* of visible copper mineralisation from 124.40 to 133.06m

CNG25 DD007: 32.3m* of visible copper mineralisation from 87.00 to 119.30m

CNG25 DD008: 21m* of visible copper mineralisation from 4.5 to 25.5m

CNG25 DD009: 12.6m* of weak visible mineralisation from 44.3 to 56.9 and 4.7m* from 109.3 to 114m

In all cases mineralisation is of high-sulphidation style and mineralogy and occurs as abundant disseminations, veinlets, crackle networks and breccia matrix fillings of hypogene chalcocite, bornite, chalcopyrite and lesser pyrite, associated with minor quartz-baryte gangue and intense quartz-alunite-dickite/pyrophyllite alteration that overprints earlier pervasive illite-montmorillonite alteration² (see Figures 1 and 2).

Zonation in the copper mineralogy is evident with mineralisation in the northern holes (DD001-005, Figure 1) being dominated by chalcocite-bornite and the southern holes (DD006-008, Figure 2) being higher in chalcopyrite and bornite. This mineralisation is visually comparable to that evidenced in the bottom of the Mostaza open-pit and historical ore stockpiles where rock sampling by GSC returned assay grades up to 4.64% Cu and 177ppm Ag³.

The mineralisation and its associated alteration occur in structurally controlled "lenses" or "lodes" of felsic porphyry, "tuffisite" and polymictic rock-flour matrix breccia. In places the lenses may be bounded by faults and/or cut by narrow inter-mineral to late-mineral andesitic dykes with intensely clay-altered margins.

These are preliminary observations, and detailed core logging and geological interpretation is ongoing.

Next steps:

Detailed geological and geotechnical logging of the core, including petrographic and spectral studies, is now underway and will be used to assist in the planning of future drill programmes and improve the understanding of the mineralising system at Cerro Negro. Core samples for holes CNG25 001 - 009 have been despatched to ALS Laboratories for analysis with the last samples delivered on 14^th February. Results for initial holes are anticipated within the coming weeks.

Planning and permitting for the next phase of drilling at Mostaza has commenced and is expected to include resource and exploration drilling. Metallurgical studies of drill core, stockpiles and tailings is also being planned.

Figure 1: Cerro Negro Project, Mostaza Mine: Photographs of drill core from CNG25 DD001. Left: Crackle and veinlet hosted chalcocite-bornite (cc-bo; black mineral) cutting illite and locally quartz-alunite-dickite/pyrophyllite altered polymictic breccia (30.4m depth). Right: 5cm thick vein of steely-black chalcocite (cc) mineralisation (33.2m depth). Bottom: Intense crackle and disseminations of black chalcocite (cc) in polymictic breccia (36.7 to 37.2m depth). All drill core is HQ diameter 6.35cm thick. Note: core photos illustrate examples of the style and textures of copper mineralisation observed within the mineralised intervals and are not necessarily representative the entire mineralised zone.

 Figure 2: Cerro Negro Project, Mostaza Mine: Photographs of drill core from CNG25 DD007, over 200m south of mineralisation shown in Figure 4. Upper Left: chalcopyrite (cpy) dominated breccia matrix within intensely silicified rock (113m depth). Upper Right: intense disseminated, crackle and breccia matrix mineralisation of purple bornite (bo) and yellow chalcopyrite (116.4 to 118.4m depth). Lower Left and right: Intense dissemination and breccia infill by bornite-chalcocite, bo-cc, (90.4m depth) and chalcopyrite, cpy, (103m depth). All drill core is HQ diameter 6.35cm. Note: core photos illustrate examples of the style and textures of copper mineralisation observed within the mineralised intervals and are not necessarily representative the entire mineralised zone.

Figure 3: Cerro Negro Project, Mostaza Mine: Long section of Lens 2 with circles showing the location of where phase 1 drillholes are projected to intersect the hanging wall of the mineralised lens. The exact intersection points are subject to confirmation. Completed drill holes are shown with their final end-of-hole (EOH) depths. The apparent thickness of visible copper mineralisation is shown in bold below each intersection point. Note that mineralisation remains open at depth and along strike. Historical resource blocks, underground mine workings, and channel sample and drillhole assay results (coloured) are shown for reference. (GSCU has not been able to independently verify the historical channel sample or drill hole assay results).

Figure 4: Cerro Negro Project, Mostaza Mine: Plan map showing the approximate locations of mineralised lenses at surface, historical drill holes, and current GSC drilling. Note the scale.

Cautionary note:

*Apparent thickness: There is not sufficient geological information to calculate true thickness of mineralised intercepts at this time.

Photographs of core and mineralisation are for visual purposes only to assist in explanation and description of mineralisation styles and textures observed in the core and do not convey any information as to the copper assay grade of the mineralisation photographed or the mineralised zones as a whole. The company will report assay grades when they are received from the laboratory and have been assessed, verified and certified.

References:

1.            RNS 2189S (06 January 2025): Diamond drilling commences at Cerro Negro

2.            RNS 7484V (04 February 2025): Drilling extends copper mineralisation at Mostaza

3.            RNS 3120K (31 October 2024): Cerro Negro Results Up To 4.64% Cu and 177ppm Ag

Enquiries:

Notes for Editors:

About Great Southern Copper

Great Southern Copper PLC is a UK-listed mineral exploration company focused on the discovery of copper-gold and lithium deposits in Chile. The Company has the option to acquire rights to 100% of two projects in the under-explored coastal belt of Chile that are prospective for large scale copper-gold deposits. In addition, the Company has the option to acquire rights to 100% of a lithium project located in the Salar de Atacama district of Chile. Chile is a globally significant mining jurisdiction being the world's largest copper producer and the second-largest producer of lithium.

The two, early-stage Cu-Au projects comprise the San Lorenzo and Especularita Projects, both located in the coastal metallogenic belt of Chile which hosts significant copper mines and deposits, including Teck's Carmen de Andacollo copper mine, and boasts excellent access to infrastructure such as roads, power and ports. Significant historical small-scale and artisanal workings for both copper and gold are readily evident in both exploration project areas.

The Company's Monti Lithium project is strategically located in the pre-Andean region of Salar de Atacama which is Chile's premier lithium-producing region with well-established lithium mining operations and infrastructure.

Great Southern Copper is strategically positioned to support the global market for copper and lithium - both critical battery metals in the clean energy transition around the world. The Company is actively engaged in exploration and evaluation work programmes targeting both large tonnage, low to medium grade Cu-Au and Li deposits as well as high-grade Cu-Au deposits.

Further information on the Company is available on the Company's website: https://gscplc.com

Competent Person Statement  

The information in this announcement that relates to exploration results is based on and fairly represents information reviewed or compiled by Mr Sam Garrett, a Competent Person who is a Member of the Australian Institute of Geoscientists and a Fellow of the Society of Economic Geologists. Mr Garrett is the CEO and a shareholder of Great Southern Copper PLC. Mr Garrett has sufficient experience that is relevant to the styles of mineralisation and types of deposit under consideration and to the activity being undertaken to qualify as a Competent Person as defined in the 2012 Edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves". Mr Garrett has provided his prior written consent to the inclusion in this announcement of the matters based on information in the form and context in which it appears.

This announcement includes information that relates to Exploration Results prepared and first disclosed under the JORC Code (2012) and extracted from the Company's previous LSE announcements as noted, and the Company's Prospectus dated 20 December 2021. Copies of these announcements are available from the LSE Announcements page of the Company's website: www.gscplc.com.

The Company confirms that it is not aware of any new information or data that materially affects the information included within the Prospectus dated 20 December 2021.

Forward Looking and Cautionary Statements

Some statements in this announcement regarding estimates or future events are forward-looking statements. They include indications of, and guidance on, future earnings, cash flow, costs and financial performance. Forward-looking statements include, but are not limited to, statements preceded by words such as "planned", "expected", "projected", "estimated", "may", "scheduled", "intends", "anticipates", "believes", "potential", "predict", "foresee", "proposed", "aim", "target", "opportunity", "could", "nominal", "conceptual" and similar expressions. Forward-looking statements, opinions and estimates included in this report are based on assumptions and contingencies which are subject to change without notice, as are statements about market and industry trends, which are based on interpretations of current market conditions. Forward-looking statements are provided as a general guide only and should not be relied on as a guarantee of future performance. Forward-looking statements may be affected by a range of variables that could cause actual results to differ from estimated or anticipated results and may cause the Company's actual performance and financial results in future periods to materially differ from any projections of future performance or results expressed or implied by such forward-looking statements. So, there can be no assurance that actual outcomes will not materially differ from these forward-looking statements.