Notes on Monhegaii Island. — Lord. 345 
gabbroitic intrusions have been termed beerbachyte (aplitic 
gabbro), and the dioritic, malchyte, (apHtic dioryte). 
It is of interest to note that oHvine, the prevaiHng ferro- 
magnesian constituent of the olivine-noryte, is lacking in the 
dike rocks, and, further, that feldspar no longer preponderates 
over other ingredients. » 
Beerbachyte (5, 6, 10. 16) consists of an even granular 
mass of diopside, hypersthene and bytownite, in about equal 
proportions, associated with magnetite and a few scattering 
grains of apatite. These ingredients differ only structurally 
from those described in connection with the olivine-noryte. In 
many of the specimens (i, 2, 3, 13, 14, 24, 26, 27) brown horn- 
blende, identical with that of the hornblende gabbro, enters 
into the composition of the rock; sometimes to the almost 
complete exclusion of the pyroxene (2, 24, 26). This brown 
hornblende and more especially the pyroxene, is, furthermore, 
frequently replaced by green hornblende, as a result of uraliti- 
zation. which is not readily distinguished from the primary 
amphibole of the malchyte . (See below ) \ 
A peculiar feature of the beerbachyte as well as of other 
rocks of the region is the frequent occurrence of veins and 
seams of secondary green hornblende. These were at first 
supposed to be magmatic segregations, but on close inspection 
they were found to follow continuously the joint and rift 
planes in the rock, which would indicate that uralitic horn- 
blende is not necessarily of prescribed local development, but 
may, under favorable conditions, occur along independent 
zones of fracture metamorphic agencies have been most 
active. 
Chlorite and limonite are the principal products of atmos- 
pheric weathering of these rocks. 
Malchyte (4, 7, 9, 11, 20, 21, 23, 25, 28, 29) is dark steel 
gray in color, and of even granular structure, very similar to 
beerbachyte. The rock is composed essentially of dark green 
hornblende and bytownite, with accessory biotite, magnetite 
(pyrite) and apatite. The hornblende is of short prismatic 
form, with the large angle of extinction (angle C: c^=about 18°), 
pleochroism (parallel c =green, parallel b^=^ brownish green, 
parallel a— greenish yellow) and absorption (c>b> a) charac- 
terizing the primary hornblende of the gabbrodioryte. (p. 338). 
