The Mill Site and Mercury

One of the most intriguing maps that has been discovered regarding the missing mining district is the Minas del Oro (Gold Mines) map.   The original is leather, but for the sake of clarity, a drawn replica is shown below, compliments of the late Tom Kollenborn.  The year that the map was created is either 1814, 1824, 1834 or 1844, as the third digit was worn off.

At first glance, this map seems to be  looking west somehow, because of the label of Rio Salado (Salt River) and the “Picacho” would naturally be Weaver’s needle.  But, the label of Rio Salado appeared to be incorrect, because most maps point north and the Salt River runs mostly east-west.

The map is trying to tell the viewer to look for a fold or “hinge” in the basalt and only one fold in the basalt was known; this is a hill that was dubbed “Cerro Negra” and is in the middle of the Molly Marie Prospect.

Minas Del Oro Map
The fold in the Basalt….”Cerro Negra” looking east

It was conceived that this map was looking north just like most maps, and the river was actually First Water Creek in First Water Canyon that flows at least 6 months of the year most years, and not the Salt River. It was also guessed that the “Picacho” was a spire by Government Well, about a mile to the northwest of Cerro Negra.  This is what the spire looks like (this is also the horse’s ear; see the Peralta Stones page:

Several hikes were made into First Water Canyon over many months, because it was a nice hike, and on one hike out of the canyon, the below  was noticed on the gated road that leads from an area with a steel awning in the canyon:

Cart Ruts

These were suspected to be ox-cart ruts, from steel-rimmed wheels.  After some research, it was learned that the awning and surrounding foundations were built in the early 1970’s as a satellite operation of the original First Water ranch which was about a mile upstream.  A small dozer was used to make a very steep road to get materials to the awning area; this was not negotiable by animal-drawn carts.  The topsoil was disturbed, and the rain did the rest; the ruts that crosscut the dozer road  were exposed over the years.   A ladder and a broom were taken there, most of the ruts were cleaned, and photos were taken from above.  The area that is circled in the photo below shows where the steel rims cut the rock.  It is estimated that these ruts were made over a period of over 100 years due to  dates on Spanish maps. It appears that heavy rains washed gravel constantly across the ruts,  and then new ones were worn by the carts.

Cart Ruts after Cleaning

Below is a diagram showing the relation ship of the Prospect, First Water Canyon, the awning, Hackberry Spring, and the cart ruts.

The Haul to the Mill Site

It was known that the Peraltas have had to use mercury to process the bonanza gold.  Without mercury, it is estimated that only about 50% of the gold would have been recovered.  It is suggested that arrastras were used, but  were only used for amalgamation.  By 1600, Mexico had 400 animal powered stamp mills in operation, and it is reasoned that they had at least one here. The ore was then crushed and amalgamated much more quickly than could be done by arrastras alone.

To test the theory that great amounts of mercury were used, a mercury vapor detector was rented (below).
Mercury Vapor Detector Testing

It was read that a shallow hole should be dug in the topsoil, and the air in the hole should be tested immediately.  This was done at Potosi, Bolivia by others to test the soil there; this is one of the most mercury-polluted places on earth due to the silver mining and patio process.  This is a link to a paper about the mercury study that was done there:

The same procedures were done near First Water Canyon and generally the same results were achieved as those at Potosi!  Below is a portion of a vapor detector database showing one of the soil testing sites at First Water and how the mercury values increased and dropped off in a shallow test hole:

Jerome Model: J405-0007
Serial Number: 405-00347
Date: 27-Oct-15 21:28:58
Gas: Hg

dd-MMM-yyyy hh:mm:ss Reading Units Temp-C
27-Oct-15 14:05:22 0.87 ug/m3 33.43
27-Oct-15 14:05:24 1.13 ug/m3 33.43
27-Oct-15 14:05:26 0.97 ug/m3 33.43
27-Oct-15 14:05:28 2.75 ug/m3 33.43
27-Oct-15 14:05:30 2.66 ug/m3 33.43
27-Oct-15 14:05:32 1.09 ug/m3 33.43
27-Oct-15 14:05:34 0.54 ug/m3 33.43
27-Oct-15 14:05:35 0 ug/m3 33.43

The phenomena that was observed just like what had occurred at Potosi. The meter would read 0 or just above 500 nanograms, and then spike to 2000 to 3000 nanograms (2 to 3 micrograms), and drop down again.  This occurred in several test holes.

A quote from the Potosi paper: “but the excavation of the topsoil causes an important release of the elemental vapor, reaching concentrations over 3000ng m−3.”  Note: This is equivalent to 3 ug/m3 on the Jerome detector.

Below is photo-diagram showing the items learned in  First Water Canyon near the awning area.  The white line is the dozer road, and the yellow is the Peralta road that was switch-backed to maintain a negotiable grade:

First Water Ranch Items

These items align well with what is shown on the Minas del Oro map. The main camp (Campo Mayor) was at Hackberry Spring.  Sunlight never touches the bottom there due to the very high cliffs running east-west .  Hackberry Spring is quite the oasis, and the spring there runs year around.

There were also very high mercury readings in the air at the satellite First Water Ranch, and especially in the creek bed itself, upstream from the awning.  It is thought that the the people that lived there and the cattle were sick most of the time from breathing and ingesting mercury.  This is what the creek bed looks like there and would correspond to the area called “Placeras” on the map.

First Water Canyon Creek Bed

The creek bed appears to have been placered and all the gravel and rocks were removed long ago.  There are no ore deposits upstream, and a theory was generated that at one time a lot of ore was processed without mercury, and the stream bed was cleaned to re-work the sand left behind.  This would have been a placer, but for different reasons than usual.  To test the theory, sand was cleared off of the higher pockets of sand in the creek bed until black sand  was exposed on the bedrock.  Then, a battery powered vacuum was used to suck the black sand up.  The sand was taken home, panned down, and the magnetite was removed. What remained was manganese minerals and Golden Barite.  The manganese minerals and the Barite  have the same density and could not be separated in any way by panning.  Some very tiny specks of amalgam could be seen.   Barite is an important mineral found in IOCG deposits.

Golden Barite panned from First Water Canyon

Below is a picture of Golden Barite from Leadville, Colorado.

Golden Barite

Over this many-year long investigation, two different refraction seismic surveys were done.  These will be discussed further on the Seismic Work page.   In the diagram below is shown the Black Chlorite alteration and the seismic lines that indicate pits.   Each line indicated had 24 geophones to complete the survey.   This is the same place indicated on the Minas del Oro (Gold Mines) map that indicates the mines.  There are several maps that show the location of the mines of the district, but the Minas del Oro map   is the most comprehensive because it shows the location of the mill, the mines, the haul road, and the placers.  It is believed that as time progressed, the area that was mined was expanded and the Peraltas began mining underground. Although a guess, it is estimated the date on the map would be 1824.  There is little doubt that the Minas del Oro map depicts the situation at that time exactly.  It is known now that the circled area in the photo below should be much larger and it is an IOCG deposit, not a VMS deposit.

Black Chlorite Alteration and Seismic Work