174 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
very imperfect crystals of a deep-green or yellowish color, and often 
much altered into a greenish-yellow chlorite. Numerous small square 
prisms of zircon are included in the hornblende or scattered about in 
close proximity. Epidote is abundant in quite large irregular masses or 
flakes. It is of a faint, greenish-yellow color, and plainly pleochroic. 
Magnetite in this rock is not particularly abundant, though occurring 
in rather large grains. The quartz contains very numerous cavities, 
which are, however, exceedingly minute. 
This rock is very compact and hard, but works well and takes an ex- 
cellent surface and polish. It is of finer texture than the Scotch red 
granites, and bears a closer resemblance to red granite of the Bay of 
Fundy than to any other at present in the collection. If the specimen 
received at the Museum is a fair sample of the rock at the quarry, it is 
certainly a most excellent stone. | 
Hornblende biotite granite—The quarrying of this variety of granite 
is confined to rather limited areas, specimens having been received from 
but two localities, Saint George and Lincoln. The Saint George rock 
is of fine texture, and dark gray in color, nearly black on a polished sur- 
face, the dark color being due to the abundance of hornblende and black 
mica. By the unaided eye the rock is readily seen to be composed 
principally of quartz, feldspar, hornblende, and biotite, with scattering 
grains of magnetite and iron pyrites. It is quite poor in quartz, and 
under the microscope the prevailing feldspar is seen to be a triclinic 
variety. Hornblende is very abundant, and occurs in quite perfect 
crystals, which are deep green and yellow in thin sections and strongly 
dichroic. Biotite is less abundant than the hornblende, and it incloses 
numerous magnetite grains and apatite crystals. It is quite pure, and 
of a light straw color in thin sections, varying to deep brown as the 
stage of the microscope is revolved. Occasional grains of epidote and 
sphene were noticed, and, more rarely, shreds of chlorite, resulting from 
the alteration of the hornblende. Numerous grains of calcite are read- 
ily distinguished in the thin section occupying the interspaces of the 
other minerals, and the powdered rock effervesces distinctly in dilute 
acids. So large an amount of this mineral must have an important 
action upon the weathering properties of the rock. 
Lincoln. The rock quarried at Lincoln, although of nearly the same 
mineral composition, is wholly unlike that of Saint George in appear- 
ance, being of much lighter color and coarser texture. Large white and 
slightly flesh-colored twin erystals of orthoclase, quartz, hornblende, 
mica, and in a few instances grains of pyrite, are all readily distin guish- 
able by the naked eye, while with the microscope are brought to view 
the usual amounts of apatite and magnetite, with, more rarely, small zir- 
cons, wedges of sphene, and irregular grains of epidote. The sphene is 
brownish in color, and the crystals quite large. The hornblende is deep 
green and yellow, in thin sections, and some of the smaller crystals show 
quite perfect basal outlines. Biotite is very abundant and in large 
