Exploration Drilling
Imerys British Lithium have completed several phases of drilling implementing the highest QA/QC standards for a total of 2,789.5 m of reverse circulation and 841.5 m of diamond drilling. Drilling successfully delineated potentially economic lithium-mica mineralisation over an area of 1,000 x 600 m.
Initial Drilling (Phase 1)
This early-stage drilling was carried out in Q1 2019 and achieved its objective of confirmation and validation of the original reconnaissance work carried out by the team. This gave the geologists an early indication of the economic lithium mineralisation at depth and provided representative samples for metallurgical research and process design.
Imerys British Lithium successfully completed this programme of 6 no. reverse circulation drillholes which supported the evidence of a substantial deposit within the project area. The total depth drilled was in excess of 873m and was carried out using a Comacchio MC900P. This was used in parallel with a Progradex EL350 sampler to enable correct sampling procedure was followed and maintained throughout. This discipline of sampling along with the rigorous QA/QC protocol put in place by the team ensured the samples were representative. All samples were prepared for geochemical analysis at the facility in Roche prior to using a world leading contractor to evaluate the extent of lithium within the sample.
Wardell Armstrong International performed an independent review of the RC drilling programme protocol and quality control and assurance. They concluded the drilling programme generated high quality data across all intervals and all drill holes.
Upon results, Imerys British Lithium used the data provided along with earlier data collected through desktop reviews to create vertical sections throughout the area drilled. This allowed the team to carry out complex wireframing, 3D orebody modelling and a resource/target estimation.
Figure 12: Acoustic and optical analysis of Imerys British Lithium Drill Hole
Down Hole Logs
To extract the most value from the drill programmes, we have successfully conducted geophysical surveys of selected drill holes measuring the physical properties of the rocks in situ. This data enhanced our lithological and structural understanding of the mineralisation (Figures 10, 11) through delineation of lithological features and structures that will impact the resource model.
Diamond drilling
Following up the reverse circulation programme, in December 2019 Imerys British Lithium completed a diamond drilling campaign to further the delineation of the lithium mineralisation within the area. This provided whole core samples for lithological classification and structural information at depth, which would be missed using purely reverse circulation drilling. The first hole was completed on 4th December 2019 and successfully extended the economic lithium mineralisation from surface to a depth of 201m, down to an incredible 354m.
The diamond drilling carried out used a HQ3 diamond bit and a triple core barrel retrieved by wire-line winch through the drill string without the need to withdraw the drill string from the hole. The triple barrel system gives the highest recovery of 63 mm core in broken or kaolinised ground.
Imerys British Lithium and its contractor ‘Priority Drilling’ proved the efficacy of operating onsite 24 hours per day, seven days per week and drilled 4 diamond core holes in mid-winter, prior to Christmas, without accident or injury. The remote location of Imerys British Lithium’s project ensured that overnight operation did not create any disturbance to communities.
The diamond core was then processed at the facility in Roche, with the aim of enabling metallurgical research and process development. Imerys British Lithium is the only operator in Cornwall with its own inhouse metallurgical laboratory.
After winching up the triple-tube core barrel it is swung out over the trestle table to recovery the drill core.
After retrieval, the intervals, fractures and orientation are marked on the core, before being carefully placed in the core tray.
British Lithium exploration geologist logs the core prior to high resolution photography of the undisturbed core.
British Lithium exploration geologist logs the core prior to high resolution photography of the undisturbed core.
The following objectives of the diamond drilling programme were established and completed through carrying out the campaign.
Provide solid core samples for metallurgical research. By using core samples from varying depth representative samples relating to various stages of the mine plan and metallurgical variability analysis can be performed.
Establish the extent of lithium mineralisation extension at depth. The existing RC holes ended at 201 m, still within mineralisation and so the depth of mineralisation was unknown.
Provide core for determination of moisture content and density data over the depth tested. Bulk density data is a key factor in resource estimation as it allows conversion of volume to tonnes of rock.
Verify the data generated by the RC programme by twinning two of the earlier 6 RC holes. These data will be utilised by the independent geologist to declare our maiden JORC Mineral Resource Estimate. Verification will compare assay values and intervals between the twin holes for comparable meters and seek to understand the cause(s) of any difference.
Show the validity of using the cost-effective RC method on this deposit to facilitate the majority of future resource drilling.
Conduct detailed lithological, geotechnical and structural logging of the lithium nearing and other mineralisation.
Image showing Beretta T24 drilling rig.
Shallow Infill Drilling (Phase 2)
In December 2020, Imerys British Lithium employed the services of local contractor ‘GroundSearch Ltd’ to carry out a short infill programme prior. This was targeted to obtain data from the first 100m below surface to track the variability of grade within local kaolinised zones. The programme was a success and 3 holes were drilled over a 207m programme.
These samples were then analysed and inputted into the Imerys British Lithium database and subsequently the geological model. This enabled the geology team to plan and target the next phase of drilling based on the continuation of grade that had been established through this phase of drilling.
Infill Reverse Circulation Resource Drilling (Phase 3)
Imerys British Lithium undertook a 9-hole 1700m reverse circulation programme in Q1 2021. This used the services of ‘Apex Drilling’ where the programme spanned the course of 5 weeks. The max depth achieved during this campaign was 253 m and still showed significant economic mineralisation. This provided the team with sufficient knowledge of the resource and its characteristics at depth which would be impossible to obtain through other means.
From this, the team of geologists have been preparing these samples for geochemical analysis prior to adding the data to the database and modelling software. The drilling was focused around a preliminary pit design shell – leading to the creation of the shell below with all the drillholes added.
