Kambale Graphite Project

Plan showing historical and recent interim RC drill results at Kambale
Plan showing the outline of the Kambale MRE, its close association with an HLEM anomaly and recently identified, yet to be tested, priority-one EM anomalies
Oblique view looking northwest showing the twelve Kambale graphitic schist domains used to compile the MRE
‘Plan View of Classification’ extracted from the Palaris MRE Pg64 which noted that “ Large areas exist which have been unclassified which should only require a few drillholes to upgrade due to the linear drill patterns in some domains. Many of those require drilling below 200m RL to confirm depth extent.”
Cross Section N1,112,400 from the MRE Report showing multiple lens of graphitic schist and estimated block grades
Cross Section N1,112,200 from the MRE Report showing multiple lens of graphitic schist and estimated block grades

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Kambale is emerging as a credible flagship deposit of quality, dominantly fine-flake graphite justifying the fast-track evaluation adopted by Castle over 2022/23. This is in response to the widely forecast and looming supply deficit expected for this “Critical Mineral” as the World rushes to meet its clean energy ambitions.

Mineral Resource Estimate (JORC 2012)

Classification Tonnes (kt) Contained TGC (kt) TGC (%)
Indicated 5,979 542 9.1%
Inferred 9,632 863 9.0%
Total 15,611 1,405 9.0%

5% TGC Cut-Off. TGC = Total Graphitic Carbon

For full details, see ASX release dated 12 April 2023

Castle Managing Director, Stephen Stone commented:

“Castle is fast-tracking Kambale to ensure that the Project is well positioned to take advantage of the forecast looming supply deficit for fine flake graphite concentrate used in the manufacture of electric vehicle and stationary power storage battery units.

We are confident that the 35-hole, 4,100m RC drilling programme that has just commenced, our third in the past 18 months, will materially increase the Mineral Resource Estimate of 15.6Mt at 9.0% TGC containing 1.41Mt of graphite to underpin a planned scoping study. And running alongside this programme, we have just kicked-off an EM geophysical survey aimed at locating additional graphite occurrences on the broader 149km² Kambale licence. Graphitic material observed by our geologists in several termite mounds bodes well for the success of the 200-line km survey which is expected to be completed mid-June.”

Project Background

Kambale Cross Section 1,112,200mN
Kambale Cross Section 1,111,450mN
Graphite being produced during flotation test work on diamond core samples from Castle’s Kambale deposit

The Kambale graphite deposit was identified in the 1960s by Russian geologists prospecting for manganese. They undertook a program of trenching and drilled 25 holes to a maximum depth of 25m.

The mineralisation consists of north-east trending, sub-parallel zones of meta-sediment which is host to the graphitic schists. The Lower Proterozoic Birimian (~2.2Ma) meta sedimentary rocks, namely phyllites, and quartz–biotite schists, generally trend north-easterly and dip between 50o and 75o to the north west. The schists are hosted mainly in granodiorite.

The genesis of the flake graphite in Kambale is believed to be the result of high-grade metamorphism (amphibolite-granulite facies) which has converted trapped amorphous carbon into the characteristic fine crystalline layers.

Castle reviewed the historical work and a wide-spaced, regional-scale electromagnetic survey dataset inherited from previous licence holder, Newmont Limited. This work outlined a roughly elongate, northsouth orientated, ~10km-long region considered prospective for graphitic schist horizons which may host multiple lenses of graphite mineralisation, similar to what is already outlined from drilling and trenching at Kambale. These lenses or horizons can vary in length and be up to 50m wide, creating substantial deposits of graphite.

Encouraged by firm graphite prices in 2012, Castle undertook three consecutive phases of drilling comprising RAB (251 holes, 5,621m), aircore (89 holes, 2,808m) and reverse circulation (3 holes, 303m). Mapping noted occasional outcrops of manganese and graphitic schist as well as graphite in termite mounds.

In 2012 Castle undertook a very limited program of bench-scale test work on RC chips. Thereafter, little work was undertaken until the more recent improvement in graphite prices prompted a re-evaluation of the Project in early 2021.

In September 2021 Castle’s new management team reported that preliminary test work on sub-optimal near-surface, weathered graphitic schists yielded very encouraging fine flake graphite concentrate grades of up to 96.4% and recoveries of 88%. A conventional multiple grind and flotation concentration flowsheet was used. Three excavated and composited samples provided for the test work graded 12.56%, 16.09% and 17.16% total carbon.

In March 2022, a ground electromagnetic (HLEM) survey demonstrated a strong correlation between drill confirmed graphite mineralisation and zones of high conductivity. Several high conductivity zones extending well outside of the existing Inferred Resource boundary were highlighted indicating the possibility of extensions of the known graphitic schists into sparsely or undrilled areas.

In late 2022 a 52-hole 5,353m RC program was undertaken to test the interpreted steep dipping, shallow conductive plates from the EM survey. The results confirmed that the majority of the plates where due to graphite mineralisation and that the graphite continued to depths of at least 100m and likely beyond.

Logistics and infrastructure

The Project is located 6km west of the Upper West region capital of Wa which is 400km north, via good sealed roads, of Kumasi. From Kumasi it is approximately 240km south east by rail or road to the international port of Tema, 30km west of the capital Accra, which provides direct access to global export markets. An alternative international port at Sekondi–Takoradi is located approximately 230km west of Accra.

The Wa region has an excellent infrastructure comprising a commercial airport with daily flights, reliable grid power supplied partly by a hydroelectric dam at Bui, river (Black Volta River) and artesian water and many other useful services.


Ghana has a well-established mining industry including several Tier-1 mining operations. It is now Africa’s largest gold producer and the World’s sixth largest and accordingly has a well-trained and very capable workforce supported by an excellent mining services and supply sector. It is a safe and politically stable jurisdiction based on the Westminster system and has a workable Mining Act and fiscal regime.

Social licence

Castle management has spent over 14 years successfully operating in Ghana and in particular its Upper West region. The Company has established an excellent reputation for its pro-active commitment to community engagement, local employment and training, the promotion of youth and women’s development initiatives, maintaining the highest environmental operating standards and overall operating ethically and sustainably whilst carefully managing community expectations.

Prior to embarking on any specific exploration program the Company’s Ghanaian team conducts comprehensive discussions with all stakeholders to fully inform them as to the Company’s activities and to identify sites of cultural, religious, social and economic sensitivity and to appropriately mitigate any matters of concern. Compensation for access and any disruptions caused is provided at a minimum as per Ghana Mining Act guidelines. All site disturbances are rehabilitated immediately after use and in close consultation with landowners.

Graphite market

The graphite market is diverse across industrial, metallurgical, chemical and specialised areas with each sector requiring graphite concentrates with specific qualities. Deposit type, size and geometry, flake size, flake shape, grade, impurities, capital and operating costs, ability to be refined, proximity to specific markets, supply logistics, jurisdiction, fiscal regime and many other factors all combine to determine the commercial viability of a particular deposit.

The current medium to long term outlook for the broader graphite concentrates market is one of escalating demand and a looming supply deficit driven in particular by its use in the fast-growing EV battery and stationary power storage sectors. At present, there is no viable substitute for graphite.

There is an increasing proportion of natural graphite, over high CO2 generating synthetic graphite, being used in battery anode manufacture which also requires a fine flake graphite as the primary raw material. Hence, prices for fine flake graphite concentrates have shown a steady upwards trend in the past year.

The reader is directed to numerous recent publications, conference proceedings, market research papers and corporate websites of companies engaged in graphite exploration, project development or production for informed commentary and analysis of the graphite market.

Next key steps at Kambale

  1. Complete 35-hole infill and extensional drilling programme to increase the maiden MRE;
  2. Complete the current Loupe EM geophysical survey and continue to evaluate the broader Kambale licence area for additional graphitic schist occurrences;
  3. Complete Phase 2 test work to produce a commercial-grade fine flake bulk concentrate and have this material evaluated by specialists in Europe to determine its capability to produce high-value Battery Anode Material (“BAM”); and
  4. Commence a high-level mining, processing and commercialisation Concept Study which will transition into a Scoping Study as test work results and an updated MRE become available.

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