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Mike Bullivant's Diary

Day 29: Extracting Gold

Well, I feel pretty bad this morning, but the show must go on ... what with it being show business and all that! I find it very difficult to move freely but everyone's so sympathetic and understanding. I feel a right passenger. Thank goodness that making the gold-mercury amalgam won't be that time-consuming, or physically demanding.

Forming an amalgamIt turns out that Mikey managed to crush most of the rock while I was away yesterday, so we should be ready to rock (no pun intended) and roll by 10am. All we have to do today is react the gold with the mercury to form an amalgam and then recover the gold (in a purified form). To do this, you grind the crushed ore with the mercury in a pestle. In doing so, you can see the physical nature of the mercury change as it reacts with the gold in the rock. The amalgam is a grey semi-solid that looks neither like gold nor mercury. The amalgamation process is similar to dissolving the gold in the mercury, only it's not quite that simple. Most metals will form an amalgam with mercury and it's a process that's been used for years to purify metals like gold.

Potato and amalgamThe weird thing about amalgams is that it's easy to recover the original metals. All you have to do is heat the amalgam up and, hey presto, you recover both the gold and the mercury. The problem is that mercury's really toxic and we have to be careful that, by heating the amalgam, we don't force the mercury to evaporate into the atmosphere. Mikey L comes up with a really neat Rough Science way of doing it safely - using a potato. All you do is place the amalgam under a potato that's been cut in two lengthways, with a small indentation cut into one of the raw sides. Placing the indentation over the amalgam and heating the potato up, drives off the mercury and re-generates the gold. The beauty of the process is that as the mercury evaporates, it's taken up into the flesh of the potato, and never has a chance to escape into the atmosphere.

Neat eh!? By the end of the day, we've extracted and purified all of our gold using the amalgamation process. We end up with quite a sizeable nugget as things turn out.

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Photo: Mike Bullivant
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