I'm Using Bacteria To Mine Gold...

I Can't Believe I'm Out Here Prospecting for Bacteria Now...

So, I’ve officially crossed into weird prospector territory. I used to think chasing fine gold in arsenopyrite was already obsessive. But now? I’m hiking through creeks, staring into puddles of orange slime, and asking myself: “Is this the good kind of rust, or just iron-stained disappointment?”

Why? Because apparently, the only way to liberate gold from refractory sulfide ore—without turning my backyard into a toxic roasting pit or building a DIY pressure cooker—is to enlist the help of... acid-loving bacteria.

That’s right: Acidithiobacillus ferrooxidans, aka the microscopic miners that oxidize pyrite and arsenopyrite like it’s their full-time job. These bacteria thrive in acidic, iron-rich environments and naturally break down sulfide minerals. In doing so, they free the gold that would otherwise be locked away in a mineral fortress, impervious to conventional leaching methods like cyanide or thiosulfate.

Refractory ore is a real pain. It’s called “refractory” because the gold is physically trapped inside sulfide minerals like pyrite (FeS₂) or arsenopyrite (FeAsS), making it resistant to direct leaching. If you don't roast it at high temperatures to oxidize the sulfides or use extreme pressure and chemical treatments, most of the gold stays hidden. For small-scale miners like me, traditional methods aren’t just overkill—they’re impractical, unsafe, or illegal to do at home.

Here’s the kicker: if I want to buy these bacteria in purified lab form, I’d have to fork out over $1,000. Not exactly budget-friendly for backyard experimentation. So instead, I’m out here in gumboots, collecting creek mud and sniffing rocks like some kind of microbial gold whisperer.

Turns out, you can find these bacteria in the wild. They naturally grow in places where water and oxygen come into contact with sulfide minerals—like mine drainage streams, tailings, or iron-stained seeps near mineralized rock. I collected samples from a few promising sites, made a nutrient broth with iron sulfate and a pinch of fertilizer, adjusted the pH to around 1.8 with diluted sulfuric acid, and waited. A few weeks later, the greenish liquid had turned a rusty orange. Success! My own DIY culture of acidophilic bacteria was alive and hungry.

Now, after treating my ore with chemicals to extract any accessible gold, I take the leftover material and let nature take over. I create a bioleach slurry—crushed ore, water, a touch of lime to control pH, some iron sulfate, and a sample of creek slime from a promising, rust-colored streambed. With an aquarium air pump to supply oxygen and a warm place to sit (ideally around 30–35°C), the bacteria go to work. Over several weeks, they quietly oxidize the sulfides, turning the ore from dark grey to rusty red, and liberating gold that was previously unrecoverable.

It’s slow. It’s strange. But it’s incredibly satisfying to watch a biological process do what heat and pressure usually would. No gas emissions, no smelting, no environmental damage.

Of course, bioleaching isn’t without its own challenges. One of the biggest concerns is arsenic. Arsenopyrite releases arsenic when it breaks down, and if that arsenic stays dissolved in the water, it can pose a serious environmental hazard. That’s why I take steps to responsibly manage the waste. After bioleaching, I treat the liquid with hydrated lime to raise the pH. This causes the arsenic to precipitate out as ferric arsenate—a stable, solid form that can be filtered out and safely stored. I dry the sludge, seal it in labeled containers, and hold onto it until I can dispose of it properly at a hazardous waste facility.

So if you ever see a slightly unhinged bloke crouched by a rusty puddle with a pH strip in one hand and a jar of orange goo in the other... say hi. I might just be bioleaching my way to the next gold strike.

This is gold prospecting in the 21st century: part geologist, part backyard chemist, and now, apparently, part microbiologist.