The company had announced its first JORC resource of 131Mt at 8.9% TGC over the project in February 2016, making it the world’s fourth-largest, with over 40% of this resource being in the indicated category.
Black Rock’s new infill drilling results revealed a contained TGC resource of 12.7Mt, of which 1.2Mt or 8% was a measured resource and a further 5.1Mt or 40% was an indicated resource.
The largest upgrade to mineral resource size was at the Ulanzi prospect, one of three graphite mineralised structures at Mahenge, which was up 39% to 111.8Mt at 8.2% TGC.
This was on the back of a contained TGC resource of 9.2Mt, of which 1.2Mt was a new measured resource and a further 3.9Mt or 40% was an indicated resource, up 1Mt from the February study.
Resource estimates at the Epanko and Cascade prospects were unchanged with no new measured resource included, though an upcoming infill drill program over Cascades is expected to deliver a JORC mineral resource by November – with 51 holes drilled there since mid-July.
Black Rock said it expected the program would deliver an increase in resource size, but the company was aiming to increase confidence in the resources and report a higher proportion to measured and indicated mineral resources.
Metallurgical test work at the project indicated that 99% of the TGC concentrates could be processed through a relatively simple flotation method; while concentrate testing indicated that battery grade spherical graphite and high quality expandable graphite could be made.
Black Rock chairman Stephen Copulos said the resource, along with its higher grade portions of 38.7Mt at 9.9% TGC, and its straightforward metallurgy, were the key building blocks for a company prefeasibility study to be released in November.
“The September $A5 million capital raising puts the company in a sound position to continue its development programs with independent expandable and spherical graphite test results continuing to generate highly positive results and offtake interest,” he said.
Cash from the placement of over 33 million shares at A15c each was to be used on the Cascades drilling program as well as upgrading resources, securing offtake supply agreements and funding studies including some on metallurgical optimisation and the pre-feasibility study.
Black Rock expects to release a definitive feasibility study over the project in March 2017, ultimately aiming to develop the resource into a long life, low cost mining operation.
Shares in Black Rock were up 0.5c or 2.8% to 18c in early trade, giving the company a market capitalisation of $55 million.
