Some is black with schorl, some, as that of Mill Tor, white as statuary marble.
On its northern slope is a vast mass of schorl, the celebrated Roche Rock.
The black shining matter found near where are veins of tin, is schorl.
The granite is dark red, often inclosing veins of quartz, crystallized and compact, and likewise well-formed crystals of schorl.
Greisen is closely connected with schorl rock both in its mineralogical composition and in its mode of origin.
This is more especially true of chlorite, schorl, hornblende and augite.
The exterior parts of the veins consist of a bluish quartz, very compact, and uniformly containing a great deal of schorl.