Oxide of Tin (in veins in Schist or Killas)

It is very instructive to see the form of the Tin veins and, their direction with regard to the formation of the Schist or Slate, they being either straight, or curved in a remarkable manner, and usually crossing the laminæ of the Slate.

The upper specimen came from St. Agnes in Cornwall, and consists of the coarser Killas^*: the oblique position of the veins in the larger specimen shows it to be from a lower part of the primitive Slate formation than the under figure, in which they are finer and more parallel, being of a rather later formation.