Someone asked me what is meant by Dore?

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Someone asked me what is meant by Dore?

posted on Feb 26, 2010 02:53PM

Please correct my errors as I am not a Metalurgical Engineer.

Dore is the product that is produced during the initial stages of refining. It is only about 50% pure gold and silver.

Ore is rock that is rich in minerals. It is only considered ore if the value of the contained minerals is sufficient to make it economic to mine and process. When the price of minerals such as Gold rises, material that was previously considered un-mineable rock will become mineable ore because its value has increased enough to make it economically viable.

The ore, or in this case the old tailings, is fed into a ball mill which pulverizes the rock into a powder. In this case, the ball mill contains heavy steel balls that smash the ore as the mill rotates. In some applications, rod mills are used instead of ball mills. When UC reaches the stage where mining will be required, the ore will first go into a crusher in order to reduce the size of the rocks to material that can be screened and separated. The ball mill will only accept material that is quite fine.

After milling the material goes into a chemical bath. In this case cyanide is used because it is gold and silver. This is the Merrill-Crowe process that I talked about earlier.

This chemical process is the light green liquid that you see in the big drums called thickeners. This begins to separate the precious metals from the other material that is in the rock. There are as series of these thickeners which successively increase the concentration of gold and silver in the bath. In the latter stages of the process, zinc is added to the bath. The gold and silver bond with the zinc and a further separation of the minerals from the host material occurs.

The impregnated liquid then passes through the filters and a gold/silver precipitate attaches to the filter cloth because it is too big to pass through the pores in the filter cloth. This precipitate is then collected and melted and further impurities removed to produce Dore. The liquid is circulated back into the process for further treatment and recovery.

At the La Yesca plant, there is no further refining (of Dore) done because the equipment required to do further refining is very expensive. Consideration is being given to adding sulphuric acid to the process which would greatly improve recoveries. However there are logistics problems with getting the H2SO4 tankers to the site on the long, winding, treacherous roadway. Recently a truck was swept off the mountain roadway by a rock slide and the driver was killed. One of the pictures on photobucket shows the wrecked truck lying down a very steep embankment. No decision has been made yet on whether to proceed with this.

http://s873.photobucket.com/albums/ab297/gonefishing1/Mexico/

They call the concentrated material of gold and silver, Dore. It is only about 50% gold and silver. It will be sold to a specialty refinery somewhere in Mexico that will separate it into gold and silver and then further refine it into 99.9% pure gold and silver.

Of course the price received for the Dore is dependent upon the concentration of precious metals in the Dore. UC will assay every batch produced and the purchasing refinery will do likewise to confirm the value of their purchase.