Kambale Graphite Deposit
Kambale Graphite EM Survey Increases Size Expectations
- Ground electromagnetic (HLEM) survey shows strong correlation between drill confirmed graphite mineralisation and zones of high conductivity.
- High conductivity zones extend well outside of existing Inferred Resource boundary indicating substantial extensions into sparsely or undrilled areas.
- Offsetting structures appear coincident with known zones of higher grade material implying similar zones may exist in undrilled areas.
- Drilling being planned to confirm boundaries of mineralisation, zones of higher grade material and to infill Inferred Resource area.
Castle Managing Director, Stephen Stone commented “The HLEM survey at our Kambale graphite project has not only achieved our main objective of better defining the extent of the graphite mineralisation below cover but has also provided a very strong indication of likely extensions to the known resources and mineralisation.
“The next stage is for drilling to confirm all of this and to identify areas of highest quality material ahead of a major phase of test work.”
In 2012 Castle commenced graphite exploration on the Wa Project. A historic graphite occurrence about 5km west of Wa was first noted by Russian geologists whilst prospecting for manganese in the 1960’s.
Castle located the historic trenches and completed mapping, RAB, aircore and RC drilling during the first half on 2012. In July 2012 Castle announced a maiden resource estimate for its Kambale Graphite of 14.4mt @ 7.2% C (graphitic carbon) for 1.03mt contained graphite (Inferred Resource). Flotation testwork was conducted on samples of fresh and weathered graphitic schist from the Kambale deposit. Microscopic examination of some flotation concentrates indicated that the graphite flakes were up to 250 microns long.
Exploration has only tested a small part of the interpreted graphtic schist horizon at Kambale and excellent potential exists to substantially increase the current resource. RAB intercepts outside of the current resource area include firstname.lastname@example.org% TGC and 19m @ 7.64% TGC highlighting the prospectivity of the area.
Rougher flotation tests on the fresh and weathered ore samples gave a maximum concentrate grade of over 50% graphite but at low recoveries. In the size fractions coarser than 150 microns, a high proportion of graphite loss to the scavenger tailings was observed. The -150+75 micron size fraction, concentrates 1 and 2 combined, gave a 50% graphite grade at 40% recovery with 30% lost to the final tails. The -75 micron fraction gave the highest recovery (>90%), as expected from a greater degree of graphite liberation from the gangue but grades of less than 30% were achieved. Cleaner and recleaner flotation tests on the -180+75 micron size range failed to improve on these initial rougher tests. A small degree of regrinding of the rougher tail, from 180 to 150 micron top size, improved recovery but did not achieve any significant improvement in graphite grade from the rougher tail.
In order to achieve a high grade of product from the samples supplied, a grind size below 75 microns is recommended. The softness and smearing effect of the graphite on the gangue minerals, drives the need to take small size reduction steps followed by multistage flotation. The sample supplied for testing was RC chips and the RC drilling process itself may increase the smearing effect of graphite over the gangue minerals and any further testwork should be carried out on diamond drill core.
The testwork results from this initial study have shown that an upgrade to just over 50% graphite can be achieved in 1-2 stages of flotation. Further test work would be needed to determine if additional grind-flotation and/or gravity stages could increase the grade to produce a high grade graphite product.
Castle is currently seeking end user/industry participation to advance project development