Some known guano deposits.
Some interesting reading and potential sites for...stuff.
The deposit is located in Santa Cruz County about 30 miles west of Nogales.
Nothing is surveyed here with reference to sections, to the best of my knowledge,
but all is within the forest reserve. You will note that I have marked
the international boundary, and monument 129 is directly south of Pena
Blanca. I am positive of this number (129). At Casa Piedras [northwest]
I think is monument 132, and 130 or 131 is on top of the hill just due south
of the place where I found the deposit. By reference to the map inclosed
you will see a point marked " spring " in the deep canyon that adjoins and lies
parallel with the boundary line. That is where I found the nitrate, and it
extends in a northerly direction through the rough mountains nearly to the
point "tipper or little Bear Valley." There is an old and well-marked trail
from an old adobe house south directly to the monument referred to and a
group of very noticeable Indian markings close to the spring.
Two samples were submitted with the letter. Upon examination
in the Geological Survey laboratory they proved to be sandstone
impregnated with a very small amount of potassium nitrate. On
Mr. Kent's map the names of several small settlements appear, together
with locations of mines and of old adobe houses. Obviously
the region has for a long time been sparsely inhabited, and these
people may have kept horses or other stock. Thus at least some
possible organic sources of nitrate are present. It is particularly
significant that Mr. Kent should have found the nitrate near a
spring, close to which were marking
http://pubs.usgs.gov/bul/0838/report.pdf