gunDriller
8th May 2011, 02:23 PM
For me this subject is very interesting.
http://www.youtube.com/watch?v=2Lbk0RjKRP4
/\ I think this thing is placed upstream of the centrifuge.
http://www.youtube.com/watch?v=eL7CY7j8-_Q
/\ The centrifuge does the work of 100 to 1000 gold miners using pans.
A lot of gold finds are random - a hunter looks down and finds a rock with gold in it.
That inspires a bunch of gold-hunting. I thought this passage did a good job describing one of the techniques for working up from the placer deposits found in a stream, to the actual lode that the gold came from -
http://www.goldgold.com/stories/greatslabs.htm
"Each mining area also has distinctive sizes and shapes of gold particles. Some areas are noted for the size of the nuggets produced; other areas produce only microscopic particles of gold. The type of gold in the area determines the method of searching for it.
All placer gold originated in a lode vein. If large nuggets were found in the stream placers, they sometimes led to fabulous lodes. The early miners discovered many valuable lode mines and pockets by following the placer leads.
As a vein of gold weathers and wears away over the centuries, gold will spill down the hill or mountainside, spreading in a V-shaped pattern as it migrates down to the nearest stream. Some pockets produced only a few ounces of gold. Others, such as the famous Gold Hill Pocket, produced up to a ton of gold.
Some miners specialized in pocket hunting. They developed an inverted V method of searching for pockets. When the placer lead stopped in the stream, they started digging test holes on the hillsides. As the rows of test holes progressed uphill, the inverted V pattern was established by the holes which produced gold. The pocket of gold was found at the point of the inverted V.
Some pocket hunters worked on the theory that pockets always occurred in groups of three. When the surface pocket was worked out and the vein pinched off, they kept digging and sometimes were able to strike a second and third pocket."
So the gold is distributed in a V-pattern as it makes its way down a hill to a stream, over the years. Then the miners try to work backwards in an inverted V, to try & locate the mother lode.
But it's fairly obvious that you will probably just get a good tan and maybe a fantastic case of poison oak if you just go out and pan the same creek everyone else pans.
So, to increase the yields, some mines now set up a mechanized placer system, and they use a centrifuge to concentrate the gold, taking advantage of its extreme density.
http://www.oro-industries.com/products/centrifuge/centrifuge_oro-industries.html
http://www.oro-industries.com/_images/_equipment/_centrifuge/centrifuge1.jpg
/\ The Tool, a Centrifuge.
http://www.musclecars.net/parts/parts-images-large/two-gram-vial-placer-gold-dust-flakes-and-or-nuggets_120686943476.jpg
/\ The Goal - Gold Dust
As it turns out, extracting gold flakes from a mud slurry that is gold-rich involves working with mesh sizes -
"RECOVERY: “If you can pan it we can recover it". A “skilled panner” can recover free gold down to 100 mesh. And our Low-G Centrifuge has equal ability for free gold recovery. However, in a production environment, recovery rates using gravity separation methods for gold particles down to 200-300 mesh begin to decline using any gravity separation method. We claim 99% recovery of free gold down to 100 mesh and 80% to 90% recovery down to 200 mesh. Recovery rates of free-gold particles at 300 mesh minus start getting out of reach of physical concentration means and require chemical separation methods. 300 mesh gold is almost colloidal and tends to stay in suspension in the turbid water. Even in clear water, this ultra fine gold stays in suspension almost indefinitely with the high water flows in a production environment. Claims of high recovery rates of 300 mesh gold in a production environment using physical (gravity) means are simply not true."
It sounds like, once the gold particles get too small, then you need to use chemical methods to separate them.
One thing I learned is that in the "olden days", the first Gold Rush in California & Oregon, in areas where they had enough rain, they would carve canals into the hill-side, 1000 feet up from the area they wanted to explore for gold. Then the water would rush down the canals, and be channeled into a tube 100 to 200 feet above the mining claim. So they would basically end up with the equivalent of a fire hose amount of water, which they would use to dig away the creek-bed or hillside to find more good sludge/sand/rock to run through their sluices, looking for those juicy nuggets.
http://metaldetectingworld.com/07_photogallery/singles/gold_nuggets.jpg
I thought this miner's log from 1869 was interesting -
"The mines are therefore directly dependent upon the duration of the season of rains. This lasts usually from December 15 to June 1. The mining season for the year ending June 30, 1869, was, however, here, as elsewhere, a very short one, owing to the extreme dryness of the winter. The season opened about the loth of January, and was over by the middle of May. When I visited the county, early in August, nothing was doing except by some of the Chinese, who were painfully overhauling the dirt heaps and carrying the earth to water. The average annual product of Jackson County in gold dust for the last five years has been, according to good authority, $210,000. I estimate the product for the year ending June 30, 1868, in spite of the brevity of the season, at $200,000, since the patient labor of the Chinese, of whom there are a considerable number working for themselves, has made up the deficiency of the season. They have produced not less than $75,000 during the year referred to. The product for the calendar year 1868 is practically the same as I have given, since the period of active operations fell wholly within 1869."
In 1869 the gold mining companies hired a hundred or so Chinese laborers; today they use a centrifuge.
I find myself rooting a little for the Chinese laborers. I'm sure they were watched closely but I hope they smuggled some good gold out for themselves.
http://www.youtube.com/watch?v=2Lbk0RjKRP4
/\ I think this thing is placed upstream of the centrifuge.
http://www.youtube.com/watch?v=eL7CY7j8-_Q
/\ The centrifuge does the work of 100 to 1000 gold miners using pans.
A lot of gold finds are random - a hunter looks down and finds a rock with gold in it.
That inspires a bunch of gold-hunting. I thought this passage did a good job describing one of the techniques for working up from the placer deposits found in a stream, to the actual lode that the gold came from -
http://www.goldgold.com/stories/greatslabs.htm
"Each mining area also has distinctive sizes and shapes of gold particles. Some areas are noted for the size of the nuggets produced; other areas produce only microscopic particles of gold. The type of gold in the area determines the method of searching for it.
All placer gold originated in a lode vein. If large nuggets were found in the stream placers, they sometimes led to fabulous lodes. The early miners discovered many valuable lode mines and pockets by following the placer leads.
As a vein of gold weathers and wears away over the centuries, gold will spill down the hill or mountainside, spreading in a V-shaped pattern as it migrates down to the nearest stream. Some pockets produced only a few ounces of gold. Others, such as the famous Gold Hill Pocket, produced up to a ton of gold.
Some miners specialized in pocket hunting. They developed an inverted V method of searching for pockets. When the placer lead stopped in the stream, they started digging test holes on the hillsides. As the rows of test holes progressed uphill, the inverted V pattern was established by the holes which produced gold. The pocket of gold was found at the point of the inverted V.
Some pocket hunters worked on the theory that pockets always occurred in groups of three. When the surface pocket was worked out and the vein pinched off, they kept digging and sometimes were able to strike a second and third pocket."
So the gold is distributed in a V-pattern as it makes its way down a hill to a stream, over the years. Then the miners try to work backwards in an inverted V, to try & locate the mother lode.
But it's fairly obvious that you will probably just get a good tan and maybe a fantastic case of poison oak if you just go out and pan the same creek everyone else pans.
So, to increase the yields, some mines now set up a mechanized placer system, and they use a centrifuge to concentrate the gold, taking advantage of its extreme density.
http://www.oro-industries.com/products/centrifuge/centrifuge_oro-industries.html
http://www.oro-industries.com/_images/_equipment/_centrifuge/centrifuge1.jpg
/\ The Tool, a Centrifuge.
http://www.musclecars.net/parts/parts-images-large/two-gram-vial-placer-gold-dust-flakes-and-or-nuggets_120686943476.jpg
/\ The Goal - Gold Dust
As it turns out, extracting gold flakes from a mud slurry that is gold-rich involves working with mesh sizes -
"RECOVERY: “If you can pan it we can recover it". A “skilled panner” can recover free gold down to 100 mesh. And our Low-G Centrifuge has equal ability for free gold recovery. However, in a production environment, recovery rates using gravity separation methods for gold particles down to 200-300 mesh begin to decline using any gravity separation method. We claim 99% recovery of free gold down to 100 mesh and 80% to 90% recovery down to 200 mesh. Recovery rates of free-gold particles at 300 mesh minus start getting out of reach of physical concentration means and require chemical separation methods. 300 mesh gold is almost colloidal and tends to stay in suspension in the turbid water. Even in clear water, this ultra fine gold stays in suspension almost indefinitely with the high water flows in a production environment. Claims of high recovery rates of 300 mesh gold in a production environment using physical (gravity) means are simply not true."
It sounds like, once the gold particles get too small, then you need to use chemical methods to separate them.
One thing I learned is that in the "olden days", the first Gold Rush in California & Oregon, in areas where they had enough rain, they would carve canals into the hill-side, 1000 feet up from the area they wanted to explore for gold. Then the water would rush down the canals, and be channeled into a tube 100 to 200 feet above the mining claim. So they would basically end up with the equivalent of a fire hose amount of water, which they would use to dig away the creek-bed or hillside to find more good sludge/sand/rock to run through their sluices, looking for those juicy nuggets.
http://metaldetectingworld.com/07_photogallery/singles/gold_nuggets.jpg
I thought this miner's log from 1869 was interesting -
"The mines are therefore directly dependent upon the duration of the season of rains. This lasts usually from December 15 to June 1. The mining season for the year ending June 30, 1869, was, however, here, as elsewhere, a very short one, owing to the extreme dryness of the winter. The season opened about the loth of January, and was over by the middle of May. When I visited the county, early in August, nothing was doing except by some of the Chinese, who were painfully overhauling the dirt heaps and carrying the earth to water. The average annual product of Jackson County in gold dust for the last five years has been, according to good authority, $210,000. I estimate the product for the year ending June 30, 1868, in spite of the brevity of the season, at $200,000, since the patient labor of the Chinese, of whom there are a considerable number working for themselves, has made up the deficiency of the season. They have produced not less than $75,000 during the year referred to. The product for the calendar year 1868 is practically the same as I have given, since the period of active operations fell wholly within 1869."
In 1869 the gold mining companies hired a hundred or so Chinese laborers; today they use a centrifuge.
I find myself rooting a little for the Chinese laborers. I'm sure they were watched closely but I hope they smuggled some good gold out for themselves.