The fact that the Miller graphite deposit is hosted in marble should also be a benefit when it comes to processing costs. I spoke with a few representatives from graphite companies at PDAC. The companies with lower processing costs pointed to the softness of their ore as being the major contributing factor.

On an absolute basis, quartz, feldspar and granite are at least several times harder than marble.

This probably also helps to explain why the Miller graphite can be purified to above 99% Cg from flotation alone.