ST ON 
tO Re ke Ue gt We ene ROSE ae Ens ee Ree ate ee Se ee eee eee ee ee 
and its Contact Phenomena. 27 
aggregate of quartz, biotite, tourmaline, and iron oxide. 
But between this horn- 
stone and the granite 
another well defined zone 
exists. This is a dark- 
gray mass which is filled 
with reticulated black 
veins. Scarcely notice- 
SS 
Sees 
SS 
SSD 
— 
S 
2. 
H 
is 
a 
HA 
oe 
ae 
lL 
wae 
vide and subdivide, giv- 
ing to the whole a fused, 
slaggy appearance. Un- 
der the microscope, how- 
ever, this mass is resolved 
he into a nearly pure mix- 
Section of tourmaline veinstone. ture of tourmaline and 
x 100 diameters. 8 
quar ile in the 
hornstone zone last described, the tourmalines are in extremely 
minute formless grains, here they are in more or less well defined 
crystals, and possess a concentrically banded structure. White, 
blue, light brown and dark brown layers follow one another in 
the order named. Fig. 2 (x 100) represents a section possess- 
Ing these zones. These crystals are bounded by the planes 
! ik. 
—-$tR—- > 22. This mass I characterize as the zone of the 
tourmaline veinstone to distinguish it from the last, or the 
zone of the tourmaline hornstone. There is reason for this in 
the circumstance that the impregnating material has wholly 
altered the character of the schist. 
The chemical changes that have taken place, both in ulti- 
Mate composition and mineral constituents, are indicated in 
the following table of analyses : 
