Ask The Experts

Free / Ask The Experts

Ask the Experts: Ionizing mercury

May 2012 by Chris

Q: I am told that “ionizing” mercury will enhance its ability to amalgamate with gold. Is this real? I understand that clean gold and clean mercury will amalgamate. Does “ionizing” (which seems to include some strong alkali solutions, such as lye) really just clean the gold, or is there something else happening here?


A: What is sometimes called “ionizing” mercury, also sometimes called activated or charged mercury, is actually an amalgam of mercury with some very active metal like sodium, potassium or calcium. Just like a normal amalgam, which is a combination of gold with mercury, “ionizing” mercury is a combination with one of these other active metals. Mercury actually amalgamates with a number of metals, including copper, silver and gold. When mercury is mixed with an active metal like sodium, potassium or calcium, the combination of the two is also reactive because these other metals are very reactive themselves.

The advantage of ionized mercury is that it can overcome coatings on the gold and mercury that often impede normal amalgamation and cause loss of gold. Amalgamation that proceeds very slowly or not at all will happen very quickly with the ionized mercury. The downside is the flammable hydrogen and lye that forms when it’s wet and the fact that it has to be made up at each use because of the reactivity of the material. “Ionizing” mercury has to be made up fresh each time it is used because it does not store well.

These reactive metals combine with the air or water to form other materials, and they will also react with any iron oxides or other materials that coat the gold. So what is actually happening here is that both the mercury and the gold are being cleaned at the same time, which promotes amalgamation between the mercury and the gold.

Mercury is potentially toxic and should be handled only with the greatest of care. Appropriate gloves, eye protection and adequate ventilation are necessities. I actively recommend against the use of mercury in capturing gold because of the environmental liability. While I know it is the old time method, there are better things out there now for the individual prospector. You will find that mercury is hard to get hold of as few prospecting shops still carry it and many chemical supply laboratories won’t handle it.

You can argue all day about how toxic metallic mercury actually is, but governmental agencies will still go nuts over it. Here in Northern Nevada, a few years back, a student brought a teaspoonful to class one day. This small amount of metal was dropped and it shut down a school for more than a month and cost over $100,000 to clean up. They now evacuate half the local university when a thermometer is dropped. It’s precisely this type of liability scenario and the lawsuits that it spawns that keep prospecting shops from acquiring or selling it. I currently recommend the use of high power, rare earth magnets and concentrate cleaning systems like bowls, wheels and other similar devices for processing black sands because they are capable of producing a product every bit as clean as can be achieved with mercury—and probably in less time.

© ICMJ's Prospecting and Mining Journal, CMJ Inc.