Mentioned in writing as far back as 300 A.D., the Philosopher's stone is a legendary substance sought by alchemists for its reputed ability to — among other things — turn lead into gold. Despite many attempts, alchemists were ultimately unsuccessful in producing the philosopher's stone, but it would appear that modern science has found it, in the form of a bacteria that can poop out pure gold.
The bacteria, Cupriavidus metallidurans, is able to consume the naturally-occurring toxic chemical gold chloride, and produce nuggets of 99.9% gold as a waste product. On Material Safety Data Sheets, gold chloride is considered a "very hazardous" skin and eye irritant, and is very dangerous if inhaled or ingested, prompting laboratory workers to wear eye protection, lab coat, dust respirator and gloves when working with even small amounts of the substance and it seems that even a full environmental suit may not be sufficient protection when dealing with a large amount or spill.
Kazem Kashefi, an assistant professor of microbiology and molecular genetics, and Adam Brown, an associate professor of electronic art and intermedia, both at the University of Michigan, have put together a combination science and art exhibit called 'The Great Work of the Metal Lover', named after 'The Great Work' — the supposed process by which an alchemist makes a philosopher's stone.
The exhibit, which looks like a giant alchemical experiment, contains the bacteria while it is fed the gold chloride, and it takes a week or so to consume the toxic chemical, leaving behind tiny spheres of gold.
The latest cost of a gram of gold in Canadian dollars, is $56.53, and depending on where you get it, you can buy gold chloride for about $25-30 a gram (or substantially less if you're willing to buy it by the metric ton), so it might be economically feasible to make money doing this — IF you already have the facilities to safely handle the chemicals, as this is NOT the kind of operation you'd want to be running in your basement or garage.
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The gold standard for currency hasn't been used since 1971, so the world economy is in no danger of collapse due to this tiny microbe, although the current advocates of that system might want to beware.