This is a previous discussion between myself and spid81.. By use...

This is a previous discussion between myself and spid81..

By use of high grade cut off 10% material below 10%, TGC will be treated as waste material. The low-grade stockpile will be put to reserve stockpile with a 6% TGC estimated grade...Higher than peer projects

Spid Quoted: Moving the cut off grade from 5% to 7.5-12% will only see a saving of US$10-20 per tonne of concentrate produced.

By increasing the cut off grade at Lindi they have optimised the project...Only a quality high-grade project can do this....Strip Ratio in stage 1 @ 3.3:1 at mining level cost of US$25 per ton of material moved to be minimal...It's the efficiency that is created at the plant level that counts...

Spid81 Quoted: All of the work with playing around with the cut off grade just to save USD$10 per tonne of concentrate, the only real saving is reducing the CAPEX,

The new mining plan has added significant complications to the mining plan, I didn't notice this until you mentioned the narrow veins that the poor contractor has to visually inspect prior to sending it to be processed,

Take the following sample, where WKT could have processed the whole section, the poor operator has 1 m of waste, then 1 m of ore to be processed, another 1.1 of waste, followed by 1.9m of ore, 0.7m of waste then 0.8 of ore.

One could say, WKT would process this whole 7.6m section, although this would reduce the annual production as the mining plan suggest the average feed to the plant is 17% TGC.

230,000 tpa x 10.1% TGC will only result in 23.1ktpa of graphite concentrate.

Whose idea was it to increase the TGC just to save USD$10?

This is going to end in disaster as the whole ore body contains such narrow veins, the 5% blend that is suggested in the mining plan is laughable.

It is suggested that cut off grade does not matter. Cut off grade does matter

Cut off grade matters as it reduces the CAPEX cost of the required plant for similar tonnage due to fewer tons at a higher grade being fed through the plant. On the back end of the project is reduces tailings.

To give an example 40,000 TPA of concentrate is required aligned with right size market concepts...The plant is designed to run 300,000 TPA per year or 36000 hours from 300 days. Ore grade is 15% TGC with recovery and mining loss reducing concentrate.

Mining loss occurs at the mining level...Weathered material /oxide material has a lower Mpa rating and in our case can be ripped by the dozer before loading to the dump truck via a shovel bucket...Mining loss 5%

The fresh material also incurs loss's which are slightly higher than weathered material from blasting and mining. Fresh material mining loss 10%

Above these two types of loss mentioned the plant proprietary process also creates a loss known as recovery...Two different types of ore fresh and weathered will alternately be fed through the same plant... The recovery rate here may even differ from weathered material to fresh material. The DFS has allowed for these losses with a 10-15% measure accuracy...

Example plant 15% TGC 300,000 TPA fresh material 90% recovery
M/l = mining loss
TGC= grade
Rec = Recovery

300,000 x .90 = 270,000 thru plant
270,000 x .90 M/l x 15%Tgc x .90 rec = 36,500 tons of concentrate

Optimising the project from using a high cut off grade....10% TGC

Will explain the cut off in another post, for now, will use a higher TGC grade from optimising the project...IMO

300,000 x .90) = 270,000 thru plant
270,000 x .90 M/l x 18%Tgc x .90 rec = 43,740 tons of concentrate

The example demonstrates why cut off grade matters. The plant size never altered however the capital intensity per ton mined is reduced. Mining costs go up milling cost stay similar...

The slide below from 2017 DFS gives a cost per ton breakdown advantage of concentrate sold...The new DFS has chosen a higher cut off grade...

Regards Croc