SteveWith all due respect the 97.8% is the purity of the grahite and this is good but needs to be purified to 99.9% area.
The grade of Lac Knife is approx. (from my memmory) 14%t to 16% in situ.
The price is determined by flake size plus purity.The larger the flake size the more valuable.
You should go read FMS NI 43-101 and that will help you undertand some basic mining terms when it comes to graphite.