Concentrate purity, upgraded purity and cost

I have purposefully left out discussion of Chinese MOUs in this thread.

Is anyone familiar with the dark arts of flotation, particularly with respect to graphite? I thought KNL's flotation recovery results were so good due to the excellent PSD as I inferred larger flakes resulted in larger hydrophobic surface area for aeration and resulted in higher recoveries.

However in assessing where to invest some additional funds I've been looking at MNS who appears to have some cores that have a much better PSD than KNL (eg. Block F south zone) and so assumed comparative flotation % recoveries at minimum. When looking at MNS metallurgical results from 31/10/14 and 15/04/14 I find this not to be the case. For example,

	Column 1	Column 2	Column 3	Column 4	Column 5
0	MNS (31/10/14)
1		Micron	Mesh	PSD	Flotation TGC %
2	Jumbo	>300	+50	63.8	94.2
3	Large	>180	+80	20.1	88.4
4	Medium	>150	+100	5.8	80.3
5	Fine	<150	-100	10.3	72.9

	Column 1	Column 2	Column 3	Column 4	Column 5
0	KNL (07/07/14)
1		Micron	Mesh	PSD	Flotation TGC %
2	Extra Jumbo	>500	+35	8.4	97.7
3	Jumbo	>300	+48	13.2	97.2
4	Large	>180	+80	28.6	96.2
5	Medium	>106	+150	23.6	95.8
6	Small	>75	+200	10.4	93.7
7	Fine	<75	-200	15.8	87.4

Is this simply poor optimisation of the flotation circuit by MNS at this stage or are there impurities such as slimes in their ore body that don't respond well to grind/flotation?

The difference between 94.2 % and 97.7% purity might seem insignificant but my Googling suggests otherwise. For example, Focus Graphite (TSX) reports:

"...the costs of purifying a 95 per cent grade graphite to a minimum battery grade of 99.95 per cent is approximately $3,000 to $5,000 per tonne. The cost of purifying Lac Knife’s 98.3 per cent grade to battery grade quality is estimated to be between $500 and $1,000 per tonne."

Ergo, to get to battery grade +99.95% such as KNL's 99.98% 1 step HF acid leach (07/10/14), it might cost a whole lot more when moving from 94.2 % as opposed to 97.7 %. This might significantly affect the price or perceived value of a concentrate when negotiating sales contracts as if the upgrading of the natural flake purity to battery grade requires an extra $3,000 per tonne compared to $1,000 per tonne this is definitely hitting your bottom line as a buyer.