Only one sample showed both green and brown varieties together. Actinolite occurs as a later, fine-grained replacement. Quartz and plagioclase inclusions in hornblende exist locally. With a few exceptions, foliation is moderately developed in both the amphibolites and hornblende gneisses. The amphibolites and hornblende gneisses contain mineral assemblages consistent with the upper amphibolite facies.
Several samples show mineral assemblages suggesting possible granulite facies metamorphism.
Clinopyroxene is the dominant pyroxene. A few samples, however, showed both clinopyroxene and orthopyroxene. These porphyroclasts may be relict igneous pyroxenes or relicts from a earlier metamorphism that has been partially overprinted. Sillimanite appears to be replacing kyanite, suggesting that this sample barely crossed the sillimanite isograd during Proterozoic metamorphism. It is unknown whether they represent a Proterozoic event, or are associated with intrusion of the Cretaceous Tobacco Root Batholith.