— 223 — 
No. 10. Macroscopically like No. 5, also microscopically, very rich in granu- 
lar augites. (Summit of Serra Geral on Estrada Nova, Santa Catharina. ) 
No. ll. Like 3. Structure basaltic rather than ophitic. (Dike cutting granite 
two kilometers below Orleans, Santa Catharina.) 
No. 12. Dar-gray, nearly black, more closely crystalline than any of the 
others, Structure decidedly ophitic. A normal diabase, (Dike, through granite, 5 
kilometers below Minas, Santa Catharina.) 
The following specimens represent another small collection sub- 
mitted to Dr. Merrill in 1906 to which his general statement about 
the character of the collection does not apply : 
(76638) (+) Diorite. Pedras Altas, Rio Grande do Sul. Compact dark greenish 
rocks too fine grained to permit a determination of their mineral composition 
by the unaided eye, but nevertheless in appearance at once suggesting a dioritic 
nature, Under the microscope they show abundant green brown hornblende, some 
brown mica, and an occasional sphene (?) in a ground of lath-shaped plagioclase. 
Three samples from this locality, one of which has clusters of brown augite and 
is much richer in iron ores than the others. 
(76639) Granite. Capao do Leao. A medium coarse stone, piokish gray in 
color, of fairly uniform texture, in which the essential constituents are readily 
determinable by the unaided eye. Under the microscope two feldspars, orthoclase, 
and a soda lime variety, are scen to make up the chief mass of the rock with 
the usual interstitial quartz and shreds of black mica, the latter being often much 
altered to chlorite. 
(76640) Granite, Railway cut near Pedras Altas, Rio Grande do Sul. A 
coarse dark gray rock with abundant phenocrysts of dull red feldspars and much 
black mica. The microscope reveals the presence of some hornblende, a little 
secondary epidote and occasional grains of a deep brown, faintly pleochroic mi- 
neral with outlines characteristic of sphene. The feldspars are in part a triclinic 
variety. 
(76641) “Metamorphic Rock’ (Sheared Diorite). Near Pedras Altas, Rio 
Grande do Sul. A compact dark greenish gray rock traverscd by small veins of 
pinkish calcite and hence effervoscing freely with acids. Under tho microscope 
it shows wn abundance of an indeterminable chloritic material resulting from the 
alteration ofa green fibrous hornblende - which may itself be secondary — a 
little quartz and patches of iron ore. In addition, abundant more or less rounded 
areas of a dull pink gray gum-like snbstance showing under crossed nicols only 
the polarization of an aggregate. After treatment of the slide with acid to 
remove the lime and other soluble minerals, a few of these areas show residual 
traces of the twin striae go characteristic of the triclinic feldspars, to one of 
which they are therefore all referred. The rock is probably an altered diorite, 
which in its turn, may have been derived from a diabase. 
(¢) The numbers in brackets are those in the Museum Register. 
