They have mentioned cyanide on their web page in the past I believe. It leaches pure Gold from their concentrates. Very common. Once the tailings have been processed to remove as much waste as possible, the leaching begins.
In the old days they would spread out a huge sheet of plastic/rubber and pile on the tailings. Then they would spray the whole pile with cyanide and catch the Gold filled run off. It has been done away with at that scale for the most part due to contamination of local ground and ground water.
In placer mines, mercury was the poison of choice. That is no longer legal on a grand scale, but still used in a more controlled environment. In Alaska we used shaker tables and mercury, no cyanide for us.
This is just a quess.
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