It will come as no surprise that the world is littered with minuscule particles of various rare chemicals, including especially valuable ones, such as precious metals.
What might surprise you, however, is that certain precious metals are almost guaranteed to be found in certain places. Let’s take platinum, for example.
While you might think of it as an especially expensive jewelry material, platinum and its relative palladium - both referred to as platinum-group metals - are actually most commonly used in the automotive industry. More specifically, they are a vital component of catalytic converters, a device in a car’s exhaust system that helps to convert harmful emissions such as carbon monoxide into less nasty ones, like nitrogen and water vapour.
So, if platinum is present in exhaust systems, could you find it on the side of the road?
One guy recently decided to test this out. Cody Reeder, a Utah State University geology student and creator of educational YouTube videos on the channel Cody’s Lab, literally swept up a bunch of debris from the side of a highway, and set to work.
“Ultimately the platinum particles are going to be incredibly small, possibly even just a few atoms in size,” Reeder warned as he sifted the original material - full of gravel and the occasional cigarette butt - down to an superfine dust.
Instead of trying to extract a large amount, he started by testing the concept with a small sample, taking only 146g of the finely sifted roadside dust.
To get to the platinum, he added a mixture of sodium carbonate to dissolve the rock, as well as borax for thinning, and lead oxide with a bit of flour to form lead metal in high heat, causing the platinum to form a lead alloy and sink to the bottom of the container.
To separate a noble metal from something like lead, you can use the ancient process of cupellation, which involves applying high heat to melt the lead, but not so high to melt the noble metal, such as platinum.
Reeder ended up with a tiny ball of platinum 0.58 mm at its widest point. (Watch the whole process with detailed explanations in the video above).
After precipitating the extracted platinum chemically and running some numbers, Reeder concluded that for every metric tonne of the finely sifted dust he tested, you’d end up with 6.7 grams of platinum.
“That would be considered a valuable ore, actually,” he says.
At current prices, 6.7g of platinum could fetch you around $220, except collecting and refining a tonne of dust probably wouldn’t make it cost-effective.
Street dust isn’t the only place to look for scarce valuables, though. These days all our e-waste - from a bricked iPhone to a smashed telly - contains rare earth minerals, as well as gold, silver, palladium and other metals.
As with gravel, the amount in any one device is minuscule, but overall it amounts to a significant volume of precious metal, giving you all the more reason to not just toss an old phone into the rubbish, but deliver to an e-waste recycling facility where it can be recovered.
And just last year, geologists in the US demonstrated that the sludge in our sewers has no shortage of precious metals, either. “The gold we found was at the level of a minimal mineral deposit,” Kathleen Smith of the US Geological Survey told The Guardian.
One kilogram of sewage can contain 0.4mg gold, and a whopping 28mg of silver, thanks to the various uses of nanoparticles in everyday products.
So, one person’s trash can literally be another person’s treasure - you just need lots and lots of trash to get there.