Australian strategic metals company Pilbara Minerals in June announced a significant increase in the Joint Ore Reserves Committee- (Jorc-) compliant high-value lithium content of its Pilgangoora tantalum- lithium project, in Western Australia’s Pilbara region.

The updated mineral resource includes a 23% increase in contained lithium oxide (Li₂O) and a 6% increase in contained tantalite, based on information calculated from 19 new holes. Recent drilling has also clearly indicated the substantial potential for the resource to grow further.

The overall Pilgangoora mineral resource comprises 11.3-million pounds of contained tantalite and 237 000 t of contained Li₂O, with the recent successful extensional drilling adding 45 000 t of contained Li₂O to the inferred resource category.

The recent drilling and interim resource upgrade has also allowed Pilbara to estimate an upgraded exploration target for the Pilgangoora project, demonstrating that it is on track to delineate a globally significant hard-rock tantalum-lithium deposit.

The next phase of resource extension drilling at Pilgangoora, which is currently ongoing, started in late April and focuses on the central and southern domains, which are outside of the currently defined mineral resource. Drilling in these zones is expected to underpin further increases in the resource inventory.

The Pilgangoora project comprises five tenements, including two exploration licences and three mining leases covering an area of 31 km2, which are prospective for tantalum and lithium mineralisation.

The project is located immediately north of and along strike from ASX-listed Altura Mining’s Pilgangoora lithium deposit, which hosts a Jorc-compliant resource of 25.2-million tons at a Li₂O grade of 1.23%.

Jorc Resource Estimation
This updated Jorc-compliant mineral resource for the Pilgangoora project incorporated all historical data, including Pilbara’s 2014 drilling programme and the new information from the drilling programme completed from March to April.

The estimation was carried out by independent resource consultancy Trepanier, resulting in the estimation of inferred and indicated resources. The reporting of all domains capturing material above 0.01% tantalum pentoxide (Ta₂O₅) results in an indicated and inferred mineral resource estimate totalling 23.8-million tons at a Ta₂O_{5 content of 0.021% containing 11.3-million pounds of Ta2O5. Within the Ta2O5 resource, there is a corresponding lithium resource of 20.5-million tons at a Li2O grade of 1.16% containing 237 000 t of Li2O.}

The envelope was wire-framed using both geological logging information, in particular log- ging of zoning within the peg- matite, and assay data for Ta₂O_{5 and Li2O. Further, there were insufficient samples analysed to allow Li2O mineralisation to be populated into one of the 18 domains.}

Another five domains are significantly lower grade and are excluded – hence, the different tonnage reported above for the Li₂O resource.

If a lower lithium cutoff of less-than 1% is used in reporting, this results in a reduction in tonnage but provides a significantly higher- grade resource of 12.73-million tons at a Li₂O grade of 1.42% containing 181 000 t of Li₂O.

Importantly, the bulk of this is confined to the central zone and the newly defined south-western pegmatite.

After the current programme of reverse circulation (RC) drilling is completed, the next phase of drilling will concentrate on in-filling the resource in 50 m × 50 m spacing to convert inferred resources to indicated resources and include known extensions to these higher grade portions within the overall resource estimate.

Updated 2015 Exploration Target
Owing to the current estimation of the mineral resource being in excess of 23-million tons based on the RC drilling completed to date, Pilbara Minerals has updated its exploration target for the Pilgangoora project to between 50-million tons and 60-million tons between 175 parts per million (ppm) and 225 ppm of Ta₂O_{5 and Li2O grades between 1.2% and 1.5%.}

Pilbara Minerals executive director Neil Biddle says the Pilgangoora project is continuing to grow in size, quality and significance with each round of drilling.

“This interim upgrade builds on the March resource update and, importantly, delivers a significant increment to the high-grade lithium resource,” he highlights.

“Our latest work has also clearly demonstrated the broader potential of this deposit, with the company announcing a 50-million-ton to 60-million-ton exploration target which gives investors a good indication of its potential as one of the world’s largest and highest grade hard-rock lithium deposits.