Ann: BKT Cascades prospect delivers 12.1% TGC high grade resource, page-10

I think you're right, but from my understanding there is a small correlation based on the differing melting points of mineral compounds. The purity of the carbon is derived from the heat source as higher temperatures burn off the impurities during metamorphosis, whereas the flake size is based on the time exposed to the heat source. If there are intrusions within the deposit it can lock in some of the heat (and reach higher temps) which helps to lengthen the 'cooking' time, but certain impurities will remain if higher temperatures are not reached regardless of cooking time.

I'll keep reading up in case my understanding is wrong.