Graphite is developed as an accessory mineral as laminated aggregates dispersed through schistose and siliceous metamorphic rocks. Graphite is an opaque mineral with six-sided form and crystallises in the hexagonal system with rhombohedral symmetry. It has a perfect basal cleavage and thus presents as flat flakes. These have a metallic lustre. Graphite is found as both flakes (>70µm) and a finer grained amorphous, microcrystalline type. Graphite has a dark streak and is visually obvious in core.

At Woxna, the lattermost is the dominant type, associated with prominent pegmatite intrusions that are interpreted to be the heat source during contact metamorphism. The pegmatite intrusions comprise quartz, orthoclase and phlogopite and intrude a metamorphosed, highly strained stratigraphic succession dominated by sedimentary and volcaniclastic protolithologies, which have undergone later brittle fracturing.

The graphite deposits occur beneath a thin blanket of Quaternary age moraine deposits. The graphite and minor associated pyrrhotite are excellent conductors that allow for prospecting using geophysical methods.

Graphite mineralization occurs in prehnite bearing meta-tuffs, garnetiferous meta argillites and pegmatitic gneiss in at least three discontinuous, stratiform graphite pyrrhotite horizons.

The property has a thin overburden layer and near surface mineral resource. Consequently the conventional open pit mining method previously used at Kringelgruvan continues to be the most suitable and economic method to restart mining. The Kringelgruvan open pit mining method, which includes drilling, blasting, loading, and hauling, is designed for multiple open pit phases throughout the LOM. Drilling and blasting will be required on all of the mineral resource and waste rock. Drilling is planned to be performed using conventional downthe-hole hammer rigs capable of single pass drilling. Blasting will use commercial bulk explosive (emulsion) with down-hole delay initiation. A hydraulic shovel will load 40 tonne off-highway haul trucks.

The crushing was carried out by a contactor and the equipment is no longer available. Options for the crusher include purchasing and operating or contracting out the crushing operation. GBM proposes that the crushing plant is owned and operated by Woxna.

The design is based on crushing test work by Metso in 2012. Metso reported that the sample is abrasive but the crushability is easy. The slippery low-friction nature of the graphite in the material has been taken into account in selecting the liners. The product from this plant will be 80 % passing 6.35 mm to maximise the throughput of the rod mill.

The ROM material is fed at 70 t/h directly into the ROM bin by a mine haulage truck or from the ROM stockpile by a front end loader. The ROM has a top size of 600 mm. The ROM is screened by a vibrating grizzly to remove minus 60 mm particles. The oversize is fed into a jaw crusher where it is crushed to minus 88 mm. The grizzly undersize and crushed products are transferred by conveyor to a triple deck vibrating screen where it is screened at 8 mm. The oversize is conveyed to a bin and then fed by a vibrating feeder to a cone crusher. The crushed product is conveyed back to the triple deck screen. The crushed product screen undersize, which has 80 % passing 6.35 mm, is transferred either to the fine ore bin, or using a stacking conveyor stored in an emergency stockpile adjacent to the crushing plant. Finely crushed product can be loaded by a front end loader from the emergency stockpile onto the silo feed conveyor via a chute when the crushing plant is down for maintenance.

There is no longer intermediate storage and conveying to the rod mill and therefore, this equipment requires replacing with either an undercover stockpile or silo to prevent freezing of the crushed material. GBM proposes a new fine ore bin is installed as part of the new feed delivery equipment with sufficient capacity that the crushing plant need only be operated for approximately 4 hours every 12 hours.

The rod milling is used to ensure that there is no overgrinding of the graphite. The milling circuit consists of the existing rod mill and new cyclones. The mill is in closed circuit with cyclones to produce a product with 80 % passing 275 µm. The throughput of the mill is calculated to be 21 t/h. The existing mill is 2.7 m diameter and 3.75 m long. It requires a new 360 kW motor to maximise the throughput.

The crushed material from the bin is fed onto the rod mill feed conveyor by one vibrating feeder at a controlled rate of 21 t/h. The mass flow is measured by a weightometer on the conveyor belt which controls the feed rate to the mill. The mill discharge is screened by a trommel with the oversize being collected in a bin for recycling to the mill feed on a batch basis. The undersize is pumped to cyclones for classification at 80 % passing 275 µm. The cyclone underflow flows by gravity to rod mill feed box for regrinding. Water is added to the mill feed to ensure that the density of the slurry in the mill is 80 % solids. Water is added to the mill discharge to produce the correct slurry density for the cyclones.

The cyclone overflow is pumped to the flash flotation cell.

The proposed beneficiation process is simpler than used previously. The old process included multiple flotation stages with regrinding, sizing and gravity separation. The new circuit will use only flotation with regrinding, comprising of flash/rougher/scavenger flotation with two stage rougher concentrate cleaning with regrinding and three stage scavenger concentrate with regrinding.

The cyclone overflow is pumped to the flash flotation where high grade coarse graphite is floated. This concentrate is reground in a vertical type mill to liberate gangue minerals before being upgraded twice in column flotation cells with the concentrates being reground before being floated. The tailings from the final column is recycled to the preceding column and the tailings from the first column is treated in the scavenger cleaner circuit. The concentrate from this is then pumped to the concentrate holding tank. The flash flotation tailings is treated in mechanical rougher flotation cells. The concentrate from this is recycled back to the flash cell. The rougher tailings is treated in a scavenger flotation circuit comprising of mechanical flotation cells. The initial concentrate is reground and pumped to the mechanical scavenger flotation cleaner cells. The second concentrate is recycled back to the feed to the scavenger cells. The scavenger tailings is pumped to a holding tank. The scavenger cleaner concentrate is cleaned a further two times in flotation columns. The concentrates are reground before being refloated. The tailings are recycled to the preceding flotation cell. The final scavenger concentrate is pumped to the concentrate holding tank.

A new flash flotation cell is proposed to recover coarse graphite flakes as soon as possible. Since the existing Sala/Denver rougher/scavenger and scavenger cleaner flotation cells are in very poor condition, GBM is proposing that they are replaced by new mechanical and column cells. New cells will last longer than reconditioned ones, have better control, and produce better flotation characteristics, resulting in improved recovery and grade. For the PEA, GBM is using new cells. Three flotation columns were historically used for cleaning the fines, of which two are suitable for reuse with some minor modifications. It is there proposed that two columns existing are reused, and two new columns are installed as the cleaner cells. The wash and air require improving.