REG - Aterian PLC - High Grade Li2O and Rio Tinto Exercise JV Rights

AterianAnnouncement

10/07/2025 07:00

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RNS Number : 4215Q  Aterian PLC  10 July 2025

10 July 2025

 

Aterian Plc

("Aterian" or the "Company")

 

High Grade Li(2)O from Initial Drilling and Rio Tinto Exercise JV Rights

 

Aterian Plc (LSE: ATN), the Africa-focused critical minerals exploration and
development company, is pleased to announce positive results from the recently
completed initial drilling campaign on the HCK Project, Rwanda, held under the
Joint Venture ("JV") with Rio Tinto Mining and Exploration Ltd ("Rio Tinto").
Rio Tinto has also notified the Company of its decision to exercise its Stage
1 earn-in rights under the Joint Venture Agreement.

Highlights:

·    Rio Tinto to exercise its Stage 1 earn-in rights under the JV
Agreement, resulting in a 51% Rio Tinto interest in the HCK Licence.

·     Rio Tinto may earn up to a further 24% (to 75%) by completing
exploration expenditures totalling US$7.5 million over a follow-on period of
up to three years.

·    Successful diamond drilling completed across two targets (HCK-1 and
HCK-2), with a total of 1,180.10 metres drilled from four holes.

·   Multiple pegmatite intersections are reported on the HCK-1 target,
with downhole thicknesses up to 79.44m.

·    Notable assay result from MWOG0002 includes 6.90 metres from 174.60m
grading 2.11% Li₂O, containing a higher-grade interval of 3.45 metres at
3.20% Li₂O from 174.60 to 178.05m.

·      Drilling was conducted on only two of the twelve defined prospect
areas.

Aterian CEO, Simon Rollason, commented,

"We are highly encouraged that Rio Tinto have exercised its Stage 1 earn-in
rights following the completion of the initial Stage 1 exploration programme.
We are delighted with these initial drill results, which confirm the presence
of spodumene-bearing lithium pegmatite at the HCK Project, and in the case of
the fresh pegmatite intersected in hole MWOG0002, associated with high-grade
lithium.

The intersected widths are variable, as expected with pegmatites; however, the
drilling reveals target pegmatite bodies of appreciable thickness, up to 80m
(downhole depth). In this phase, only two of the twelve prospects identified
during Rio Tinto's fieldwork were tested, and the potential exists to identify
less weathered areas where additional spodumene-bearing pegmatites may occur.
The holes collared on HCK-1 all encountered multiple pegmatite intersections,
while the hole on HCK-2 did not hit pegmatite, missing the down-dip extension
of the extensive artisanal working on the surface.

While further work is required to fully assess the project's scale and
continuity, these early indications provide a strong foundation to build upon
as we advance our exploration activities in Rwanda. This drill phase is
considered scout or reconnaissance in its level of detail, testing only a
limited strike length, but indicates that spodumene-bearing pegmatite occurs
on the project. Good thickness of pegmatite is observed in several
intersections at HCK-1, and when fresh spodumene-bearing pegmatite was
intersected, the lithium grade is highly encouraging. The Company will provide
further updates as exploration progresses."

Joint Venture Update

Rio Tinto Mining and Exploration Limited (Rio Tinto) has informed the Company
of its decision to exercise its Stage 1 earn-in rights under the Joint Venture
Agreement, resulting in their earning a 51% interest in the Licence. The JV
has incurred a total expenditure of US$4.732 million since its inception in
August 2023 to date.

 

This decision enables Rio Tinto to complete its broader regional exploration
activities in the surrounding areas. Rio Tinto may earn up to a further 24%
(to 75%) by completing total project exploration expenditures of US$7.5
million over a follow-on period of up to three years. The Company will receive
a cash payment of US$ 100,000 from Rio Tinto at the start of Stage 2.

 

Next Steps

The initial results confirm the presence of high-grade lithium mineralisation
and demonstrate the prospectivity of the HCK Project. Additional work is
planned to further evaluate the scale, continuity, and development potential
of the mineralisation given the weathering profile. A comprehensive technical
review is currently underway to determine the optimal next phase of
exploration. A JV decision regarding the forward work programme is anticipated
by the end of 2025.

 

Joint Venture Operational Update

 

After a successful exploration programme comprising several phases of
geological mapping, geochemical sampling, and ground-based geophysics over the
2,750-hectare permit in southern Rwanda, a short diamond drill programme was
completed on 2 of the 12 prospect areas defined by Rio Tinto.

 

Three holes were drilled to test the HCK-1 target, and a fourth hole was
drilled on the HCK-2 target.

 

 Figure 1. HCK location map showing mapped surface geology, drilled targets,
 and drill hole collars.

 

 

Observations

 

Drilling at HCK-1 confirmed the presence of spodumene-bearing pegmatite, with
fresh spodumene-bearing pegmatite intersected at 170 m depth in MWOG0002.
Coarse spodumene crystals up to 15 cm, averaging 3-4 cm, are observed.

 

 Figure 2. MWOG0002. Spodumene mineralisation from 170.12-180.5m. Greenish
 laths up to 15cm long, varying from 3-4cm average laths and "matrix" style
 mineralisation with some albitisation in an upper 4m zone.

 

Multiple barren pegmatites were intersected in MWOG0003, with apparent widths
up to 80m, and with variable mineralogy. However, it also confirmed a deep
weathering profile with kaolinisation of pegmatites down to 100 to 200 m
depth, and variable geometry and thickness of pegmatites along the 250 m
strike length tested.

 

 Figure 3. Drill hole sections from HCK-1 show the pre-drilling geological
 interpretation and the results from the recent diamond drilling.

 

 

Figure 3, above, illustrates the pre-drilling geological interpretation
cross-sections at HCK-1, featuring a main pegmatite zone dipping steeply to
the west. The new drill holes are plotted, highlighting the observed down-hole
geology and extensive depth of weathering, which shows a more complex setting
with multiple pegmatites of variable strike length and thickness.

 

MWOG0004 failed to intersect the pegmatite target at HCK-2. A second proposed
drill hole at HCK-2 was not drilled as the new geological model, after
MWOG0004, suggested it would not intersect pegmatite. Additional groundwork
and interpretation are required prior to further drilling at HCK-2.

 

The drilling has revealed that the subsurface weathering profile is more
extensive and reaches greater depths than previously anticipated, particularly
in areas associated with structural features such as faults and narrow shear
zones. This enhanced understanding highlights the impact of weathering on the
distribution of lithium within the pegmatites. As a mobile element, lithium
can be released from the spodumene structure during weathering, providing
opportunities for its redistribution through leaching or adsorption onto clays
and Fe-Mn oxides in the regolith. These insights offer valuable guidance for
future exploration and resource modelling.

 

The drill hole collar information is tabled below:

 

 Hole No.  Target  Final Depth (m)  Easting  Northing   Elevation  Azimuth  Dip
 MWOG0001  HCK-1   251.60           798,883  9,731,169  1,823      013(o)   -80(o)
 MWOG0002  HCK-1   251.50           798,700  9,731,266  1,703      030(o)   -65(o)
 MWOG0003  HCK-1   377.50           798,876  9,731,106  1,774      045(o)   -65(o)
 MWOG0004  HCK-2   299.50           798,282  9,729,313  1,735      045(o)   -70(o)
 TOTAL             1,180.10

Coordinates are in WGS84 / UTM Zone 35S

 

A summary table of the geochemical results (given as down-hole intervals) is
tabled below:

 

 Hole No.   From (m)  To (m)  Interval (m)  % Li(2)O  Note
 MWOG0002   174.60    181.50  6.90          2.11      Intersected below the influence of weathering. Only fresh rock pegmatite
                                                      intersection recorded in the hole.

                                                      In total, nine pegmatites intersected down hole, varying from 0.70m to 11.30m
                                                      in width (downhole thickness)
 Including  174.60    178.05  3.45          3.20

 

 

Main observations from other drillholes:

 

 Hole No.  Target  Li(2)O (%)  Comments
 MWOG0001  HCK-1   N/S         No significant Li(2)O results from six weathered pegmatite intersections.
                               Widths (downhole thickness) vary from 0.73m to 24.77m.
 MWOG0003  HCK-1   N/S         No significant Li(2)O results from 12 weathered pegmatite intersections.
                               Widths (downhole thickness) vary from 0.67m to 79.11m.
 MWOG0004  HCK-2   N/S         No pegmatite intersected. Country rock metasediments are variably weathered to
                               the end of the hole. The collar location needs to be moved.

N/S - no significant assays returned

 

Summary of Work Completed on the Project by Rio Tinto

 

Since the start of the JV, Rio Tinto has completed the following:

 

 Geochemistry           Number of Samples  Notes
 Rock-Surface Sampling  257                Systematic surface pegmatite and metasediment samples
 Soil sampling          2,643              Permit-wide 400 x 200m spaced soil samples. Infill auger soil sampling over
                                           key areas (HCK-1 and extension, Kigarama, Kinunga North, Karambo-Murambi,
                                           HCK-2 and Gatwaro) at 20m to 40m spacing.
 Additional test work   336                290 surface samples of muscovite analysed by pXRF.

                                           35 rock samples from 2023 Q4 mapping submitted for ALS FTIR to provide clay
                                           mineralogy of weathered pegmatites. 11 selected pulps of rock samples from
                                           2023 Q4 mapping submitted for semi-quantitative XRD analyses at ALS Australia.
 Geophysics             Line km            Notes
 Ground Magnetics       246.03             100m section spacing NE-SW (045(o))
 Ground Radiometrics

 

Sampling Methodology and Analysis

 

Cut half-core samples were dried on site in Rio Tinto's mobile preparation
laboratory in Kigali. The samples were then crushed to <2mm, with a 250 to
500g split of the crushed material shipped to ALS Loughrea, Ireland, for final
preparation. At ALS, the samples were pulverised to 85% passing -75 μm before
a split is taken for analysis.

 

Samples were analysed at ALS, undergoing:

·    Four acid digestion with ICP-MS (MS61).

·    Lithium borate fusion prior to acid digestion with ICP-MS (MS81).

·    Whole Rock Analysis - Fused bead, acid digestion and ICP-AES (ICP06).

ESG Related Activities

 

2,000 trees and 1,000 grass plants were donated to the Rwaniro Sector for
Umuganda (a Rwandan tradition of community work, held on the last Saturday of
each month, where citizens participate in mandatory service for the betterment
of their communities) by Rio Tinto. The replanted area included the previously
rehabilitated artisanal mine workings, drill pads, and part of the drill site
access road.

 

Qualified Person

 

The technical disclosure in this regulatory announcement has been approved by
Simon Rollason, Chief Executive Officer of Aterian Plc. He is a graduate of
the University of the Witwatersrand in Geology (Hons) and a Member of the
Institute of Materials, Minerals and Mining, with over 30 years of experience
in mineral exploration and mining.

 

- ENDS -

This announcement contains information which, prior to its disclosure, was
inside information as stipulated under Regulation 11 of the Market Abuse
(Amendment) (EU Exit) Regulations 2019/310 (as amended).

 

Engage with the Aterian PLC management team directly by asking questions,
watching video
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Navigate to our interactive investor
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For further information, please contact:

 

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Aterian Plc:

Charles Bray, Executive Chairman - charles.bray@aterianplc.com
(mailto:charles.bray@aterianplc.com)

Simon Rollason, Director - simon.rollason@aterianplc.com
(mailto:simon.rollason@aterianplc.com)

 

Financial Adviser and Joint Broker:

Novum Securities Limited

David Coffman

Colin Rowbury

Tel: +44 (0)207 399 9400

 

Joint Broker:

SP Angel Corporate Finance LLP

Ewan Leggat / Adam Cowl

Tel: +44 20 3470 0470

 

Financial PR:

Bald Voodoo - ben@baldvoodoo.com (mailto:ben@baldvoodoo.com)

Ben Kilbey

Tel: +44 (0)7811 209 344

 

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Notes to Editors:

About Aterian plc

www.aterianplc.com (http://www.aterianplc.com)

 

Aterian plc is an LSE-listed exploration and development company with a
diversified African portfolio of critical metals projects.

Aterian plc is actively seeking to acquire and develop new critical metal
resources to strengthen its existing asset base while supporting ethical and
sustainable supply chains as the world transitions to a sustainable, renewable
future. The supply of these metals is vital for developing the renewable
energy, automotive, and electronic manufacturing sectors, which are
increasingly important in reducing carbon emissions and meeting global climate
ambitions.

 

The Company has entered into a joint venture agreement with Rio Tinto Mining
and Exploration Limited. Rio Tinto will earn into the HCK project in
southern Rwanda, exploring and developing a lithium-tantalum-niobium-tin
mining operation. The Company also holds an exploration licence in Rwanda.
Aterian has a portfolio of multiple copper-silver (+ gold) and base metal
projects in Morocco. Aterian owns a 90% interest in Atlantis Metals, a
private Botswana-registered company holding seven mineral prospecting licences
for copper-silver in the world-renowned Kalahari Copperbelt and three for
lithium brine exploration in the Makgadikgadi Pans region.

 

The Company's strategy is to seek new exploration and production opportunities
across the African continent and to develop new sources of critical mineral
assets for exploration, development, and trading.

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