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Notes on Brazilian Igneous Rocks by Geo. P, Merrill 
The rocks are all of the diabase-basalt type, presenting no essential diffe- 
rences except in structure. The most interesting mineralogical feature is their 
poverty in olivine which is in most instances completely lacking. 
No. 1. Fine grained, uniformly dark-gray rock without porphyritie consti- 
tuent of any kind. Under the microscope a dense aggregate of pale augite and 
rather stout plagioclase, with the ophitic structure usual to diabase. There is 
the usual scattering of iron ore. 
The rock is very fresh and decomposition products rare. (Vertical dike near 
Bonito I, Minas, Santa Catharina.) : 
No. 2. Even more dense than No. 1. Under the microscope a similar mi- 
neral composition, but the structure more basaltic and iron ore in proportionally 
greater quantities. (Horizontil dike immediately overlying the Barro Branco 
coal bed on Rio Passa Dois, Santa Catharina). 
No. 3. Does not differ materially from No. 1. (Vertical dike near mouth of 
rio do Rasto, Santa Catharina.) 
No. 4. Acompact brown-gray rock in which none of the constituents are 
determinable by the unaided eye. Under the microscope, an aggregate of muddy 
augite and lath-shaped plagioclases, with the usual iron oxides. Structure 
basaltic. (Base of eruptive series on Estrada Nova (‘), Santa Catharina.) 
No. 5. Dense uniformly dark-gray without constituents recognizable to the 
unaided eye. Under the microscope essentially similar to No. 4. (Estrada Nova, 
Santa Catharina.) 
No. 6, Dense dark-gray, with uniformity of color and texture broken by 
occasional amygdaloidal cavities (1 to 10 mm.), some of which are filled and other 
empty ; filling material sometimes quartz and again an undetermined zeolite. 
Under the microscope augite and plagioclase with abundant iron ores and 
yellowish glass. This shows an original amygdaloidal cavity filled with chlorite 
and other scondary minerals (Basalt), (Middle of cruptive flow, Estrada Nova 
Santa Catharina. ) 
No. 7, A dull-brown, ocherous, highly amygdaloidal rock, too much rotted 
for satisfactory study. The microscope shows little but lath-shaped plagioclase 
imbedded ina yellow-brown glass plentifully besprinkled with iron oras (Basalt). 
(Estrada Nova, Santa Catharina. ) 
No. 8. Like No. 1 in appearance. Under the microscope an abundance of 
small granular augite in a ground largely crystalline, of lath-shaped plagioclase. 
An occasional granule of olivine (?). (Estrada Nova, Santa Catharina.) 
No. 9. Nearly black and somewhat vitreous, appearing, under the micros- 
cope, a black glass full of opaque dust and beautifully curved and dendritic co- 
lorless microlites, and carryang pale augite granules, plagioc!ase, and iron ores, 
the latter, in part, at least, Titanic (Basalt). (Estrada Nova, Santa Catharina.) 
(*) Estrada do rio do Rasto, 
