SME Presentation

On February 25th, 2020 a presentation was given by myself at the national conference of the SME (Society of Mining, Metallurgy, and Exploration) at the Phoenix Convention Center, and it was called “Mid-Tertiary IOCG deposits in Arizona and a “Lost” mining district”.  This was a challenge, because over 15 years of fieldwork and research had to be rendered down to 20 minutes and 22 slides.

The presentation is given here slide by slide, with the bullet points that were presented:

SLIDE 1

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  • Welcome everyone.
  • My presentation is about a “Lost” mining district in the Superstition Mountains area about 35 miles east of here, and it is a culmination of 15 years of study and research.
  • People have been looking for 130 years for lost mines or a “mine” in the Superstition Wilderness area, but the mines are not in the wilderness area.
  • Widely varying stories told of pit mines and underground mines.
  • The oldest printed story that I’ve read about lost mines in the area was printed in the Phoenix newspaper in 1893, and it was about prospectors that had found a “Great Mine” just north of Superstition Mountain with many shafts, and what appears to be described as a large subsidence zone.  The prospectors then wandered up to the Goldfield area to find something much greater the story said.
  • The next oldest study that I’ve read was from 1895 by a writer named Bicknell in a San Francisco Paper.  Bicknell interviewed dozens of people in this area from all ethnicities, and the consensus was that there was a mine with an 80-foot shaft, and that the mine was in a “District”.  In 1895 there was only one kind of district, and that was a mining district; this is an area where there are many mines.
  • Over time, the story devolved until it became a tale of one mine, and people forgot what the word “District” meant. 
  • The term “The Lost Dutchman”, did not even surface until 1952, when a book by the same name was published.
  • This photo is of the north side of Superstition Mountain, and in the broad area of the photograph, 400 of a Peralta-led party were massacred by Apaches in 1848, at the end of the Mexican-American war. The party was hiding mines that had been mined by the Peralta family from northern Mexico since the early 1700’s. The Americans had just taken what is now the southwestern part of the U.S. from Mexico.

SLIDE 2

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  • Some may say, “How can an entire mining district be “Lost” outside the Superstition Wilderness area given today’s technology?”
  • This is a map of the Mineral Potential of the Superstition Wilderness and the surrounding area prepared in 1981 by the U.S. Bureau of Mines. 
  • 1981 was the beginning of the greatest down cycle in mining since the last depression, and this study was likely forgotten about.
  • The red areas have high mineral potential and are outside of the wilderness area.
  • The red area to the southeast is where the great Resolution deposit was discovered in 1992.
  • The red area on the west end has had little or no exploration since 1981. 
  • The “G” in the red area marks the historic gold mining district of Goldfield.
  • The “X” in the red area marks location of the Molly Marie Prospect

SLIDE 3

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  • The Molly Marie Prospect is a group of 20 contiguous mining claims sited on a collapse caldera over one mile in diameter.
  • The red lines outline the group of claims
  • A collapse caldera is created when the magma chamber of a volcano evacuates and the rock above it collapses.
  • In this case, the volcano was then eroded to its base.

SLIDE 4

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  • This is a google earth photo of the Goldfield mining district located only 2-1/2 miles away from the Molly Marie Prospect.
  • The Goldfield District is also sited on a collapse caldera and the volcano here was also eroded to its base. 
  • The brown areas on the margin are breccias. Breccia consists of fragments of rock that are created when the center of the caldera collapses, and the rock fragments are ejected around the margin of the caldera.  Breccias are an excellent host for ore.
  • Only a few mines that were in the Goldfield District are labeled here.  They are all located in breccias, and were all located on the perimeter of the collapse caldera.
  • The Mammoth Mine was the largest. It was discovered in 1893 when a flash flood exposed mineralization in Weekes Wash. A shaft was sunk and the Mormon Stope was struck only 35 feet below the surface.  The gold ore ran hundreds of ounces of gold to the ton.  The stope was 20 feet wide and 200 feet long.  The grade continued to the 400 foot level, and the mine reached the depth of 1022 feet below the surface.  Even here, the grade was still .66 ounces of gold per ton.
  • The Old Wasp claim labeled here had a major strike in 1983.  A vein 8 feet wide was struck with a backhoe.  The vein was heavy with galena, and a one-foot wide portion of the vein ran 244 ounces of gold and 50 ounces of silver per ton.  A million dollars worth of gold at 1983 prices was removed from a small open stope near the surface.
  • These two mines are just examples of the bonanza gold found in Goldfield.

SLIDE 5

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  • Now, back to the Molly Marie caldera. The slide is a highly enhanced google earth photo of the caldera created to accentuate the iron alteration.
  • The reddish areas are breccias that are found in multitudes greater abundance than those found in Goldfield.  The red areas have highly magnetic soil as evidenced by the inset on the lower left. Just by kicking the soil and dropping a magnet on it produces instant results.
  • Please note the spot marked with an “X” and the hill dubbed “Cerro Negra” .  These will be talked about in detail.

SLIDE 6

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  • Many disturbed areas were found in the brecciated areas of the Molly Marie caldera that were suspected to have been mined by others by surface pits and filled back in.
  • These disturbed areas were suspected to have been the same type of orebodies that were mined in Goldfield.
  • A seismograph was rented twice from a company called Geometrics to investigate the possibility.  The refraction method was used on 12 locations in total.  The data was screened by rented software, and the data from 8 locations was sent to a geophysicist for further analysis.
  • This slide is a tomogram from the spot marked with an “X” in the previous slide, and was prepared by Zapata geophysics in Denver.  This represents a pit 40 feet deep, 120 feet long, and the area is about 80 feet wide.
  • All 8 areas that were screened and had the data processed further by geophysicists indicated pits.
  • Even though the outcrops of the orebodies have been removed, an alteration zone remains that surrounds each orebody. 
  • The inset in the upper right shows what the alteration looks like.  The normally tan-colored arkose of the Whitetail formation has been altered to black chlorite, a type of mica.  This type of alteration is commonly found surrounding the sub-seafloor portions of VMS deposits in Canada, but it was learned that it also surrounds the perimeter of a cousin of the VMS ore deposit, the IOCG (Iron Oxide Copper Gold deposit).

SLIDE 7

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  • This is the Molly Marie Prospect ore genesis model.
  • 20 million years ago, southern Arizona was covered in deep brine lakes, because the Colorado River had not been formed yet.
  • Occurring concurrently with the brine lakes and adjoining them was the Superstition volcanism.
  • There are 3 main types of IOCG deposits, and this is the caldera type.
  • Brine is more saline than seawater, is highly corrosive, and it dissolves the metals from the volcanic debris of the volcano.  In the model, the solution percolates through the volcanic debris, surrounding rock, and the breccias and boils off near the magma chamber.  The metals precipitate at the boiling zone in the breccias and beneath the layer of basalt in the caldera.
  • The breccias are a great “trap” for metals because the rock fragments chemically react with the hot metal-laden brine causing them to precipitate.  However, beneath the basalt exists and even better trap. The basalt is an aquaclude stopping the upwelling hot brine, and the upper portion of the Whitetail formation contains a high amount of limestone.  The limestone neutralizes  the acidic solutions causing the metals to precipitate.
  • The inset on the upper right shows the rock that is found at the volcanic neck.  It is a rhyolite porphyry that is very high in iron and can be highly magnetic.  This porphyry is pre-enriched in metals by nature and is what the volcanic debris was comprised of. This is likely to be the #1 reason for the gold richness of this IOCG.
  • The inset on the lower right is the massive hematite porphyry found in large outcrops at “Cerro Negra”. Massive hematite and magnetite is predominant in IOCG deposits.
  • Supergene gold is also in the model.  Supergene gold is created after the brine lakes subside and residual salt dissolves the gold in the ore, carries it downward, and the gold is precipitated at the water table.  This process creates incredibly rich gold deposits, and this is what the now filled-in pits were focused on.

SLIDE 8

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  • After the seismic testing was done, it was concluded that many filled-in pits were located in the breccias beyond a reasonable doubt .
  • If all this ore was mined, it had to be processed somewhere nearby.
  • Of all the old maps “out there” only one showed a processing area (Arrastras), and this was the “Minas del Oro” map, or “Gold Mines” map in this slide. 
  • This was found to be the most comprehensive map in existence.  It is made of leather and the third digit is worn off, so it could be from 1814, 1824, 1834, or 1844.  Many experts have concluded that this map is authentic.
  • The river labeled Rio Salado was believed to be incorrectly named, because the Salt River runs east-west, and most maps have north at the top.  It was believed this had to be First Water creek that flows in First Water Canyon most of the year except for droughts.
  • “Negra” is the center piece of the map and appears to be a fold in the basalt.
  • Please note certain features on this map, as it will be shown on a google earth photo where their locations are.  Notably, the locations of the Negra, Picacho, Campo Mayor, Arrastras,  Camino, Placeras del Oro, and Minas will be shown.

SLIDE 9

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  • This slide is a google earth photo of the area represented by the Minas del Oro map.
  • The spot that is “Negra” is the hill dubbed “Cerro Negra”. This is the only fold found in the basalt for miles around. 
  • The “Campo Mayor” corresponds with a place called Hackberry Spring.  This spring flows year-around, and it is located at the foot of a 500-foot tall cliff.  This cliff is orientated in a direction so the sun never hits the bottom as can be seen by the shadow in the photo.  This is quite the literal oasis, and is the perfect location for the main camp.
  • The place that labeled “First Water Creek” was suspected to be where the arrastras (crushers) where located.
  • The spot labeled “cart ruts” will be shown in detail, and this spot is located on the large “Camino”(road) on the Minas del Oro map.
  • The “Placeras del Oro” (gold placers) were suspected to be in First Water Canyon, and will be shown in detail.
  • The “Minas” on the map were suspected to be the pits that were proven seismically and geologically. The arrastras in First Water Canyon were about one mile away.

SLIDE 10

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  • This is the “Picacho” shown on the map, and is just northeast of the “Minas” shown on the Minas del Oro map.  Some call this Gonzales rock.

SLIDE 11

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  • This is “Cerro Negra”, the hill that is the great fold in the basalt.  This is looking east.

SLIDE 12

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  • After taking several hikes into First Water Canyon to prove my suspicions, ruts were noticed in the road that were suspected to be cart ruts (the photo labeled “before”).
  • A broom, camera, and tall stepladder were brought out to clean the ruts and photograph them from above, and the photo labeled “after” was gained.
  • Note the circled area where there are flat grooves created where the wheels rolled over a small ledge.  It can be seen that these were created by steel rims.  The other grooves were filled with gravel after rains and the wheels ground out the debris forming rounded grooves.
  • The hill and road behind the camera in the “before” photograph is very steep (>25%) and could not be negotiated with carts.  The carts had to “zig-zag” down the hill.  This zig-zag is even shown on the Minas del Oro map.
  • The road shown was made in the 1970’s by a small dozer making a road to the satellite First Water Ranch. The dozer disturbed the topsoil, and monsoons did the rest.  The Peralta’s must not have known that they existed beneath the topsoil, or they would have removed them.

SLIDE 13

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  • The cart ruts were evidence of countless loads of ore being hauled down to First Water Creek for processing.
  • The ore absolutely had to be processed using amalgamation and mercury or approximately 50% pf the gold would have been lost.
  • A mercury vapor detector was rented to test the air and soil in the area.
  • A research paper was found about testing the soil in Potosi, Bolivia for mercury.  Potosi is likely the most mercury-polluted place in the world due to the use of the patio process for recovering silver. Potosi was the worlds #1 silver producer.
  • In Potosi, small holes were dug, and the “sniffer” of the mercury vapor detector was immediately put in the hole, and the soil briefly exhaled mercury vapor.
  • The same method was used on a large flat area near the creek by the satellite First Water Ranch, and an extremely high amount of mercury vapor was detected. As can be seen in the slide, the vapor started at .87 ug/m3, peaked at 2.75 ug/m3, and returned to 0, all in 13 seconds.  These readings were almost identical to that found at Potosi, and this same level of mercury vapor was found in several holes.

SLIDE 14

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  • The vapor detector was taken to First Water Creek about 75 yards away, to see what readings could be obtained in the open air. 
  • The creek bottom there appears to be thoroughly cleaned to bedrock, by placering.
  • The alarm on the vapor detector did not sound off continuously, but it sound off frequently in the open air for hundreds of yards upstream of the awning shown in the google earth photo. 
  • It was only 90 degrees outside that day, and this was not a good place to be due to the mercury vapor.
  • There are no orebodies upstream, and it is suspected that the ground-up ore that was processed by others without mercury was reprocessed with mercury.  This was the modus operandi of Chinese emigrants, and the reprocessing of placers was done throughout the American West by them.

SLIDE 15

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  • So now it was known where the pit mines were and where the ore was processed, but where were the underground mines?
  • It was strongly suspected they were located at Cerro Negra (the fold in the basalt).  The fold would be the best trap for gold both physically and chemically, because it is an anticline with both breccias and limestone beneath.
  • A story kind of “fell in my lap”, and it is called the “Salazar Survey” and written by Clay Worst.
  • The story begins with a man called Cristobal Peralta that visited Tucson in 1924.  He hired Perfecto Salazar of Florence as his guide and interpreter. Cristobal was from Spain, but he was raised in Mexico.
  • To make a long story short, they were driving several miles north of Apache Junction on Apache Trail (now Highway 88) and Cristobal had Perfecto pull over.
  • Cristobal pulled out a large map and proceeded to tell Perfecto that in 1853, five years after the massacre, the Peralta’s returned to the mines and conducted a clandestine mining operation.  They brought surveyors, and a photographer, even though photography was in its infancy.
  • Perfecto did not remember much from the map (he didn’t tell anyone about this until 1949)
  • Perfecto wrote the numbers 4 and 62 on a paper bag afterwards that he remembered were prominently displayed on the map.
  • Clay Worst tried to solve the mystery in 1949, with surveying equipment, but was unsuccessful.
  • I thought the numbers could be the numerical portions of quadrant bearings; quadrant bearings were used by the Lewis and Clark Expedition and I used them when surveying 40 years ago.  This method in hardly used anymore, or possibly not at all.
  • It was suspected that the full quadrant bearings would be N4E and S62E, and they were referencing Cerro Negra, and were the bearings to two prominent landmarks from Cerro Negra.  It is an age-old technique to give a location of a place in no-man’s land with the bearings to two landmarks.  Where the bearings intersect is the location.
  • One of the suspected landmarks was a tiny hole though the top of a mountain shown in the inset.  This hole can be seen just before sunrise all along First Water Road on the north side of Superstition Mountain and disappears when the sun comes up.  It is made for Hollywood.
  • The second landmark was suspected to be El Sombrero or Weavers Needle.
  • Working the locating technique backwards, the brunton compass in the inset was taken to the top of Cerro Negra to take the bearings to the landmarks. The declination was set to 0. This cannot be solved with google earth because Cerro Negra is highly magnetic and the compass is turned considerably there; the bearings have to be taken physically from Cerro Negra.
  • N2E and N65E were the bearings taken by the brunton to the tiny hole and El Sombrero respectively.
  • These were 2 and 3 degrees off respectively from the Salazar numbers.
  • But, the magnetic declination has changed by 3 degrees since 1853 as learned from NOAA.
  • When the 2017 numbers were adjusted for declination as shown in the table in the slide, the bearing to the tiny hole was off by one degree, and the bearing to El Sombrero was exactly the same. 
  • Considering Salazar gave whole numbers to begin with, and the brunton is accurate to within a half of a degree, the numbers are a perfect match.
  • The bearings give the exact location of Cerro Negra, and it is impossible that what has been described occurs by coincidence.

SLIDE 16

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  • Salazar said that Cristobal Peralta showed him three small glass photographs with “El Sombrero” in the background of each of them.  They were taken at different distances from the mine on the same bearing.
  • Weavers Needle looks like a hat in a very small area.  Salazar specifically said “El Sombrero”.
  • This slide is a replication of how he describes photo #2.  That is Cerro Negra in the center.  Bicknell described the mine as being within a 5-mile radius of Weavers Needle.  The distance to Cerro Negra is 6 miles. This is looking in the direction of the bearing of S65E in 2017.
  • There is a strong suspicion that Cristobal and Perfecto walked to Cerro Negra. It is only a 20 minute hike from the highway.

SLIDE 17

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  • All attention now turned to Cerro Negra.
  • Cerro Negra had always been viewed in normal plan view on google earth
  • By rotating google earth to a south looking position, and lowering the viewing angle, it was shocking to see what appeared to be large subsidence zone on the east side of Cerro Negra created by a caved stope. It was especially surprising since a center post for one of the Molly Marie mining claims had been set in the middle of the crater 10 years before.
  • The only mining method known for the time period that would work on multiple passes on a thicker soft orebody is called the top-slice method. It is no coincidence that this method was used for centuries to mine hematite in England.
  • The inset in the lower left shows what the outcrop looks like on the ridge on the north side of Cerro Negra.  The rock is volcanic tuff, and it is tipped into the subsidence zone. The tip of “Flatiron” can be seen in the distance.
  • Note the spot labeled “portal” as it will be shown later. This was discovered a couple of years ago in the summer during a bad drought.  Bees were flying in holes between rocks at the base of a short cliff there.  After backing up a hundred feet or so and throwing rocks at the spot, it was known that the bees were after water and it wasn’t a bee hive. Later that winter, a hole was dug at the base of the cliff, and a “brow” was encountered and a large void was found under the brow. It was filled with dried saguaro fruit from packrats.  It was concluded that it was a portal.
  • Note also the area labeled “saddle”.  This photo doesn’t do it justice, but the saddle is a literal highway across the canyon and the subsidence zone.

SLIDE 18

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  • This is what the subsidence zone looks like up close.  It looks like it happened yesterday.  The saddle is to the upper right, and El Sombrero can be seen over the top of the ridge. 
  • The inset on the lower right shows how magnetic the rock is in the subsidence zone.  This is a washer magnet and it easily stands on edge on the magnetic rock.  It can also be seen how the rock is saturated by quartz veinlets.
  • Magnetism seems to be a great indication of ore on Cerro Negra.  Wherever there are apparent cave or subsidence zones (especially here and on the south side of Cerro Negra) the rock is highly magnetic within each one.  This may be indicative of a boiling zone and/or convection cell beneath. All of these areas are suspected to be caved stopes.

SLIDE 19

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  • So, are there any maps that seem to indicate multiple shafts like the 1893 newspaper article?
  • Yes, there is.  The  Burbridge map was found hidden in the cover of an old book in Mexico in the 1960’s.  It was read that this map was truly dated to the 18th century by the University of Arizona.
  • The map is of an apparent mine development project that lasted four years, 1749-1753.
  • The copy of the map did not have the Salt River on it and the trail leading from it that are on the original.  These were added in red. 
  • The title is a mixture of Portuguese, Latin, and Spanish.  Ona is Latin for “District”. The full translation is “The Esteemed People of the Salt River District of the North.”
  • The map shows a workers camp for men and one for women.  This is indicative of forced labor.
  • The Pima revolt was in 1751, and pretty much ended the forced labor of native people by the Spanish and Jesuits.  It is suggested that the people that were being separated against their will were Chinese. (another story)
  • It is suggested that the reason the trail labeled is “footprint trail” is because the trail was made by people with no wheels and no horses (pre-columbian miners).

SLIDE 20

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  • This map shows the Burbridge map laid over a google earth photo of Cerro Negra.  The “pass” and the edge of the rhyolite were used as anchors when expanding the map.  The map was not rotated.
  • The contact zone of the Rhyolite and the basalt is important because beneath the basalt the Rhyolite contacts the upper Whitetail that has much limestone.  These are excellent conditions for gold skarn deposits.
  • This may not seem important here, but please note the location of the shafts labeled 1, 2, and 3 that will be shown later.
  • This is the dubbed the Burbridge Level of the mine, or the upper level, and will be explained further.

SLIDE 21

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  • This is the Ortiz map and was given by an Apache man to a rancher near the Salt River, Ortiz.
  • The Apache man said the map was taken off a dead prospector that the Apaches had killed.
  • The oddity of this map is the date of 1884.  All mining should have been long before that.
  • It is very important to note the spot where it appears there is a portal with water draining out of it. 

SLIDE 22

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  • This is the Ortiz Map overlain on the Cerro Negra photo.
  • The portal spot shown earlier and the edge of the Rhyolite were used as anchors.
  • This map was not rotated when overlain.  It is clear that this map was surveyed and due north was used.
  • The tunnel passes exactly beneath the ridge on the north side of Cerro Negra.  This ridge is an anticline as described previously, and for several reasons is the perfect gold trap. 
  • The drift to the north runs right next to the contact zone of the rhyolite and the basalt (and the limestone-laden upper Whitetail below).
  • The drift to the west is just beneath the basalt.  The surface elevation of this area and the portal elevation checks out.
  • There is a very large subsidence zone in the “Y” formed by the tunnels on the southwest side of the hill. This area is highly magnetic.
  • The 1,2, and 3 match up with the 1,2, and 3 of the Burbridge overlay above.  The shafts were extended to the level below.
  • This is the second level of the mine, about 50 feet below the Burbridge Level.  It is now dubbed the “Ortiz Level”.
  • Like many old districts like Pachuca and Virginia City, a drainage tunnel has to be driven from farther out to drain the lower levels.  In this smaller case, the drainage tunnel was driven in ore mostly .
  • An exposure of the actual contact zone between the Rhyolite and Basalt could not be found on the west side of the volcanic neck. This contact zone is important, because gold bearing fluids may have escaped to the surface.
  • However, an exposure was found on the east side of the volcanic neck and it assayed .02 ounces of gold per ton. This is affirmation of the gold ore forming processes that took place here.

  • This is the last slide of the presentation.
  • More than a just a compelling argument has been given that a mining district can be “lost” right out in the open in plain sight.
  • There is a much more evidence that there was not time to present; please visit the Molly Marie website for more.
  • The District would have not been lost if it were not for the Mexican American War; it would have been mined out.
  • The Peralta party did an excellent job of hiding the mines.
  • There was much hatred then, and there is still some now for the U.S. after taking what are now 5 states from Mexico.
  • There is excellent exploration potential on the Molly Marie Prospect, and in the entire area. There are at least 4 collapse calderas, and Government Well deserves special attention.
  • Please see me after this presentation if you would like to talk more about the subject.

SLIDE 23

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  • The Hoddenplye map shown is another map that surfaced from Mexico in the late 1800’s.
  • This map was not included in the presentation because there was not enough time allotted, but it belongs here.
  • It shows the exact general arrangement of Cerro Negra as presented;  the tiny hole through the mountain, the placers, and Cerro Negra.  The mines apparently didn’t need any introduction on this map or the Minas del Oro map.  It must have been well known that Cerro Negra is where the mines were located.
  • This map is looking southeast and it indicates three placered areas.  About two hundred feet north of the location of the original or main First Water Ranch house there are large piles of boulders that are piled up like many placers throughout the west.  A pile of boulders is shown on the southernmost placer in the map here.  First Water Creek passes through here and it appears ore was processed here also, and the sand was later reprocessed.  This was not known when the vapor detector was rented. The main First Water Ranch is about .7 miles upstream from the satellite First Water Ranch.

SLIDE 24

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