Mercury does not hurt when it harms you. There is no burn, no pain, no bad taste at the time. The damage is to your brain and your nerves, it builds up over years, and most of it does not come back.
The danger is not touching it. The danger is breathing it. When you burn amalgam to drive off the mercury, it turns to a vapour you cannot see or smell, and it goes straight from your lungs into your blood and into your brain. Standing over the pan while it smokes is the worst thing a person can do to themselves in this trade.
This page is not here to tell you to stop mining. It is here so that you get the gold and keep your hands steady and your memory sharp. There is a way to do both, and it also saves you money.
A retort
A retort is a closed pot with a pipe out of it. You put the amalgam inside, seal it, and heat it. The mercury boils off, travels up the pipe, cools in water, and drips back out as liquid mercury you can use again. The gold stays in the pot.
It recovers around 95 per cent of your mercury. Nothing is breathed. Nothing goes in the river.
It can be made from ordinary steel pipe fittings — a threaded cap, a nipple, an elbow, a length of tube, and a bucket of water. Any welder or plumber can build one in an afternoon. Many mining associations give them away.
The catch, honestly stated: a retort takes a little longer than an open pan, and the first time it feels like a nuisance. That is the whole cost. Weigh it against the calculator below.
Every gram of mercury that leaves as smoke is a gram you must buy again. Work out what that is costing you in a year.
Then do these, starting with the next burn. They cost nothing and they matter enormously.
A cloth over your face does nothing against mercury vapour. Only distance, air, and a closed vessel work.
Two methods that work
Gravity, properly done. Gold is nineteen times heavier than water and six times heavier than the sand around it. A well-set sluice, a shaking table, a spiral or a centrifugal bowl will take you to a concentrate that is mostly gold. Most mercury is used to make up for a sluice that is running too fast, too steep, or with the wrong riffles. Fixing the sluice is cheaper than buying mercury.
The borax method — direct smelting. Take your clean concentrate, mix it with borax, and melt it. Borax lowers the melting point and takes the unwanted minerals into a glassy slag; the gold sinks as a bead. It needs a good concentrate and a furnace that reaches proper heat, and it takes practice — but it uses no mercury whatsoever, and miners in the Philippines have used it for decades on fine gold.
Neither of these is free and neither is instant. But both end with you keeping your hands steady, and neither leaves anything behind in the water.
Watch for these in yourself and in the people you work beside. They come on slowly, over months and years, which is why they are so often blamed on something else.
- A tremor — hands, eyelids, tongue. Worst when you try to hold something steady. Often the first sign, and often noticed by somebody else before you.
- Memory going — names, where you put things, what you were saying.
- Temper and nerves — irritable, anxious, shy of company, sleeping badly. Doctors call this erethism, and families usually notice it first.
- A metallic taste, sore gums, loosening teeth, more saliva than usual.
- Clumsiness — dropping things, stumbling, handwriting getting worse.
- Numbness or tingling in the hands, feet or around the mouth.
If several of these are true, the first and most important thing is to get away from the vapour. Stopping the exposure is the treatment that works. There are medicines that pull metals out of the blood, but they must be given by a doctor and they cannot undo nerve damage already done.
Tell the doctor plainly that you work with mercury. Many will not think of it, and the tests are different.
Mercury that reaches water does not sit still. Bacteria in the mud turn it into methylmercury, which builds up in fish — a little in the small ones, far more in the big ones that eat them. People downstream who never went near a mine eat it in their food.
It travels a long way and it lasts for decades. A pregnant woman eating that fish passes it to her child. This is how mining harms people who never mined.
This is the reason the Minamata Convention exists, and the reason most countries now restrict mercury. The water chemistry instrument will also tell you whether your tailings are turning the water acid, which is a separate problem that travels just as far.
Cyanide recovers more gold than mercury and does not accumulate in people the way mercury does. But it kills quickly rather than slowly, and the danger is different: a mouthful of solution, or acid meeting cyanide and giving off hydrogen cyanide gas, can kill in minutes.
It also must never be used on tailings that already contain mercury — cyanide dissolves the mercury and carries it further and faster than it would ever have gone alone. That combination is worse than either alone, and it is exactly what happens when someone reprocesses old amalgamation tailings.
Cyanide belongs in a properly built, licensed, contained operation with trained people and an antidote on site. It is not a backyard substitute for a retort.
Written for the roughly fifteen million people who mine gold by hand — the largest single source of mercury released by humans anywhere on earth, and the group least often given anything useful to read about it.
Dr. Norrie's own research included the chemistry of drainage from disturbed ground. This page is in her app for that reason.