IV.—On the Nature and Origin of the Banded Structure in the Schists and other Rocks of the Lizard District

Abstract

In my last communication, “On the Schists of the Lizard District,” published in this Magazine for April, which was meant as preparatory for the present paper, my object was to show that the rocks known as the “talco-micaceous,” “hornblendic,” and “granulitic” groups were of true igneous origin, also plutonic? and had been formed out of a common, but complex magma, and that all of these groups were made up of rocks differing widely from the types of each of them, which in some instances were seemingly due to differences in the rate of cooling, and to chemical affinity; and yet again in other instances to subsequent mechanical movements and pressure during or after consolidation.