Coarse-grained spodumene-bearing pegmatite recovered from diamond drilling.
By Sonny Rollins
Core Lithium has intersected a broad, high-grade zone of spodumene mineralisation outside the existing resource at its BP33 deposit in Australia’s Northern Territory, adding geological support to the company’s plan to restart the Finniss lithium operation.
The first hole in the latest extension program, NMRD100, returned 34.08 metres at 2.09% lithium oxide (Li₂O) from 578.70 metres, including a calculated true width of 28.50 metres, Core said in an ASX announcement issued on August 11.
The result follows an earlier hole, NMRD085, which intersected 90.17 metres at 1.80% Li₂O from 568.83 metres beyond the existing BP33 Mineral Resource Estimate. Together, the results point to continuity of the pegmatite body down-dip and along strike from the current resource envelope.
For Core, the significance extends beyond exploration. BP33 is intended to become a major underground production source in the company’s proposed Finniss restart, with additional mineralisation potentially supporting mine-life growth and future scheduling flexibility.
Drill result extends BP33 beyond current resource
NMRD100 was drilled to test extensions identified by NMRD085. The hole intersected several higher-grade zones within the broader mineralised interval:
| Drill hole | Main interval | Higher-grade intervals | Approximate true width |
|---|---|---|---|
| NMRD100 | 34.08m at 2.09% Li₂O from 578.70m | 5.28m at 2.80%; 5.40m at 2.37%; 7.11m at 2.19%; 9.83m at 2.23% | 28.50m |
| NMRD100 | 3.43m at 2.44% Li₂O from 616.54m | Separate mineralised zone | Approximately 2.00m |
| NMRD085 | 90.17m at 1.80% Li₂O from 568.83m | Previously reported extension | Not stated in the release |
The reported grades are based on diamond-drill core sampling and a 0.3% Li₂O lower cut-off for compositing, with limited internal dilution allowed. Core said the mineralised material contains coarse-grained spodumene characteristic of the BP33 orebody.
The existing BP33 resource stands at 10.5 million tonnes grading 1.53% Li₂O. Core’s latest drilling has not yet been incorporated into a revised resource estimate, and the new intersections should therefore be treated as exploration results rather than additional Ore Reserves.
That distinction is important for investors and mine planners. Mineralisation outside a resource envelope must be further drilled, modelled and evaluated before it can support a formal resource update or mine schedule. Nevertheless, the thickness and grade of the intersections provide evidence that the system may continue beyond the currently defined deposit.
Core said four additional holes are planned to test extensions down-dip and along strike from NMRD085 and NMRD100. The company is also continuing exploration at the Blackbeard prospect, where up to 12,150 metres of drilling is planned.
Diamond drilling is being used to test deep extensions of the BP33 pegmatite.
Why BP33 matters to the Finniss restart
Core placed Finniss on care and maintenance during a period of weak lithium prices and challenging market conditions. The company has since reshaped the operation around a lower-cost, longer-life underground mining strategy.
The Finniss Restart Study outlined a potential mine life of approximately 20 years, with BP33 positioned as one of the principal underground sources of ore. The study identified high-grade, steeply dipping and continuous pegmatites as a foundation for reducing mining costs.
Under the study, Core reported:
- Underground mining costs of approximately A$63–A$72 per tonne, down from A$120 per tonne.
- Processing costs of approximately A$40–A$46 per tonne, down from A$69 per tonne.
- Targeted production of approximately 205,000 tonnes per year of SC6-equivalent concentrate.
- Pre-production capital expenditure of approximately A$175 million to A$200 million.
- An updated total Finniss Ore Reserve of 10.73 million tonnes at 1.29% Li₂O.
- A broader Mineral Resource Estimate of 48.5 million tonnes at 1.26% Li₂O.
Core has said the Ore Reserve supports the first decade of the restart mine plan, while the wider resource base provides potential for longer-term extensions. The new BP33 intersections could become relevant to that second category if further drilling confirms continuity and the material is eventually converted into a resource and reserve.
The company’s managing director, Paul Brown, said the results reinforced confidence in BP33’s quality and continuity. He described the deposit as a large, continuous and uniform sub-vertical pegmatite with limited internal zoning and geometry suited to underground mining.
Those characteristics are significant operationally. A thick, continuous orebody can reduce the complexity of underground development and improve the ability to plan production panels. However, actual cost and productivity outcomes will depend on ground conditions, dilution, recovery, mine access and the final design adopted for the deposit.
Restart milestones remain separate from exploration upside
The drilling news adds potential scale to the Finniss restart case, but it does not change the distinction between exploration upside and near-term production planning.
Core’s restart guidance has pointed to recommissioning the Finniss processing plant in the September quarter of 2026, with the first shipment of newly produced spodumene concentrate targeted for the December quarter of 2026. Initial feed is expected to come from the Grants operation, while BP33 is expected to become a larger underground source over time.
Underground development at BP33 has commenced, and first ore from the deposit has been targeted for around mid-2027. Steady-state production of approximately 1.2 million tonnes per year of ore has been associated with the longer-term restart plan, with BP33 expected to play a central role.
The restart remains subject to execution, funding and operating performance. Core’s 2025 study stated that a Final Investment Decision would require Board approval and a suitable funding pathway. The company has also highlighted the importance of existing infrastructure, including the Finniss dense media separation plant and its logistics connection to Darwin Port.
Finniss combines mine infrastructure with access to Darwin Port in the Northern Territory.
What the result means for mine planners
The BP33 result creates three immediate areas of interest for the restart plan.
First, resource growth. The new intersection could support a future expansion of the BP33 geological model if additional holes confirm the same thickness and grade. The company’s existing exploration target extends down-plunge from the current resource, although Core has cautioned that the target is conceptual and cannot be treated as a Mineral Resource.
Second, mine-life potential. Additional mineralisation may provide material for later production stages, potentially extending the life of BP33 or supporting a higher level of underground output. Any such contribution would require further drilling, resource estimation, metallurgical testing and economic evaluation.
Third, mining geometry. Core’s description of BP33 as a sub-vertical and continuous pegmatite is consistent with the company’s underground strategy. The reported true width of 28.50 metres for NMRD100 is particularly relevant because true width, rather than down-hole length alone, provides a better indication of potential mining thickness.
The depth of the mineralisation also presents a challenge. Core said the broader BP33 exploration target extends to approximately 1,200 metres below surface. Testing the deepest portions may eventually require underground drilling from development areas, which would involve additional time and capital.
Processing infrastructure will be central to the planned Finniss restart.
Lithium market context
The results arrive as lithium developers continue to focus on operating costs, product quality and capital discipline rather than simply adding tonnes. The market has moved rapidly between oversupply and concerns about future battery-material demand, making the economics of restart projects particularly sensitive to concentrate prices and funding conditions.
Skillings’ 2026 lithium market outlook examines how supply responses, electric-vehicle demand and project financing are shaping the sector. For Finniss, the key issue is whether its existing plant and infrastructure can be combined with consistent underground ore feed at competitive costs.
The BP33 intersections improve the geological side of that equation. They do not, by themselves, establish additional reserves or guarantee a faster restart. The next four holes, future resource modelling and the performance of Grants during the initial restart phase will determine how much of the exploration upside can be converted into an operating benefit.
For now, Core has confirmed that BP33 mineralisation continues beyond the current resource footprint, with a wide high-grade spodumene intersection in NMRD100 and further drilling underway. That gives the Finniss restart plan a larger geological envelope to work with as the company advances toward recommissioning and longer-term underground production.
Source: Core Lithium ASX announcement: New High-Grade Lithium Drill Results at BP33