~ 
1879.) 989 [ Huntington. 
1. At Jackson Falls, and extending south to Mount Kiarsarge, 
which it seems to underlie, there is a variety of granite, which con- 
sists mainly of a feldspathic base, in which there are imbedded crys- 
tals of feldspar, generally orthoclase; these crystals rarely exceed a 
quarter of an inch in their longest diameter. Sometimes the rock 
contains a small quantity of quartz, and occasionally mica is discern- 
ible, when it very closely resembles the porphyritic granite of Von 
Cotta. This rock is largely developed in Albany, and in the Report 
of the Geological Survey of New Hampshire it is called Albany 
granite. In the area we are describing it is limited to the eastern 
part. 
2. Another variety of granite, which is the aplite of the German 
lithologists,1 outcrops on the west side of Ellis River, half a mile from 
Jackson village, at Humphrey’s ledge, on the south-west side of the 
Saco, on the west side of Iron Mountain, and it extends from the 
lode down to Rocky Branch. It consists here chiefly of an aggre- 
gate of feldspar crystals, and the quartz does not form so large a 
proportion of the rock as elsewhere. When it is not affected by 
the weather the feldspar is always of a dark greenish color, and the 
erystals are usually about an eighth of an inch in their longest diam- 
eter. In most places, however, this rock consists of feldspar and 
quartz, but there are localities where the quartz is almost altogether 
wanting, and a little hornblende is sometimes sparingly disseminated 
through the mass; sometimes, though rarely, both quartz and horn- 
blende are present. Microscopic sections of this rock from another 
locality show an aggregate of feldspar crystals which are largely 
infiltrated with quartz. At the mine we have also an ageregation of 
feldspar and rhodonite, an association that has never, to my know- 
ledge, been found elsewhere. It was first noticed by Mr. M. E. Wads- 
worth. 
3. The third variety is a typical granite, and consists of a light- 
colored feldspar, light gray quartz, and black mica. It forms a cov- 
ering over the last, except in the valleys, and occupies the summits 
of all the higher ridges north of the Saco. It is called Conway 
granite in the first volume of the Geological Report of New Hamp- 
shire. At the mine a few blasts at the upper opening revealed the 
second variety, sometimes called Chocorua granite. A few rods west, 
1 Naumann, Geognosie. I, 559. Zirkel, Petrographie, 1, 495. Blum, Lithologie, 
oder Gesteinlehre, 136. Lasaulx, Petrographie, 332. Cotta, Lithology (Law- 
rence’s translation), 333. 
PROCEEDINGS B. S. N. H.— VOL. XX. 19 FEBRUARY, 1880. 
