Two miles outside of Silverton, Colorado is the Mayflower Mill. This mill is preserved by the Historical Society as an example of how metals were extracted from ore using the flotation process.
Ore was brought to the mill from the Mayflower mine by way of an aerial tram. Details of that can be found at this blog post:
Aerial Trams in Arrastra Gulch
Prior to the implementation of the flotation process ore was processed in stamp mills where a number of weights were raised and dropped onto ore thereby pulverizing it. This pulverized ore was mixed with mercury which bonded with the valuable metals. Later the mercury was removed and recovered. A considerable amount of metal was not able to be extracted using this process and ended up in the tailing(waste) piles covering the mountain outside the mill.
The flotation process extracts 90 to 92% of valuable materials from the ores. Once this method was proven it resulted in stamp mills being driven out of business in five years.
The flotation process pulverizes ore until it is the consistency of talcum powder. This powder is then placed in long troughs which are full of water and chemicals appropriate to the metal to be extracted. Air is injected into the mixture forming large bubbles. The metals are carried onto the surface tension of the bubbles and are skimmed off.
This process captures a wide variety of metals including gold, silver, copper, lead, zinc and others.
The mill was first used to process ore from the Mayflower mine, however in later years it was used to process ore found in the tailings of former stamp mills. The flotation process extracted metals not able to be processed by the stamp mill process.
Once the mill had extracted the materials from the surrounding area it closed in the 1970's and was donated to the historical society in the 1990's.
 |
| Entrance to the mill and gift shop |
 |
| A well equipped machine shop made parts needed to keep the mill operating |
 |
| Detail of a rock crusher |
 |
| Julie in the rock crushing area |
 |
| Steel balls were placed in a crusher to help pulverize the ore |
 |
| This is an overview of the entry area and shows the benches where you watch the video about the mill and an example of a stamp mill |
 |
| This auger carried material to a rod crusher in which long bars of steel rod were rotted further crushing the ore |
 |
| The flotation tanks |
 |
| A photo of the ore powder suspended on top of bubbles in the flotation tanks |
 |
| Lots of pumps needed for the flotation process |
 |
| Security Office - due to the amount of gold processed security was needed. Oddly enough theft increased after security was installed |
 |
| Powdered ore |
 |
| Ore was vibrated over a table with multiple ridges which separated the heavier materials (Gold) |
 |
| Eventually the gold ended up in 'loafs and was about 80% pure. It was sent off to another mill for further refinement. |
 |
| Interesting place to visit. |
