564 CHWt tT: 
to those just described. A few miles to the north of Vifia del Mar, 
near the road, the hornblendic schist outcrops and presents a thin 
schistose structure with a dip to the west-by-south of seventy-five 
degrees. Three miles south of the Concon, on the same road, this 
hornblendic schist intersects the granite like a narrow dike. The 
granite just south of the Concon is almost purely feldspar. 
On the road up the valley of the Concon towards Quillota, there are 
a few schistose beds subordinate to the granite, which in hand speci- 
mens have a very ambiguous character. The rock somewhat resembles 
an argillite; it has a very fine texture and a grayish-blue colour. 
The resemblance to dikes in many of these beds of schist is ex- 
tremely close. Often the syenitic rock when rubbed, presents all the 
appearance of an earthy greenstone; yet the schistose structure 
parallel with the walls is peculiar, and distinguishes it from the 
greenstone of ordinary dikes. 
The small rounded eminence adjoining Quillota, called Mellaca 
Hill, is composed mostly of a coarse granular granite consisting of 
white feldspar and quartz with black mica. This 1s distinctly seen on 
its southwestern side, though the decomposition of the surface is so 
deep that a fresh fracture is obtained with some difficulty. On the 
northeast side, a syenitic rock crops out, composed of albite and horn- 
blende, with little quartz. The albite has a pure white colour. ‘The 
hornblende is in black prismatic crystals, often half an inch long and 
perfect in their faces; many are cruciform. The rock is compact and 
would make a handsome as well as durable building stone. Near the 
same place I obtained from boulders, apparently derived from this 
hill, a light-green rock, consisting of compact epidote with some dis- 
seminated flesh-coloured feldspar. Near by, I collected a crystalline 
limestone of a light-greenish colour; the tint was derived from minute 
oblong leafets of talc sparingly disseminated through it. Some of 
the veins in this Mellaca Hill consist of protogine, or a grayish-white 
granular compound of feldspar and compact talc; others were a 
variety of granulite ; others a compound of feldspar, quartz, and albite, 
containing some particles of magnetic iron, and a few slender crystal- 
lizations of tale. 
In the ridge designated the third cuesta on the road from Quillota 
to San Felipe, there is the same passage of granite to syenite. 
A few miles east of San Felipe de Aconcagua, towards the foot of 
the Andes on the route to the Jaguel Valley, there is an isolated 
granitic ridge, the rock of which consists of white albite and horn- 
blende of a greenish-black colour, resembling the variety of syenite 
