Preston Winter was cleaning out his late grandfather's garage in Floodwood, Minn., when he found four plastic jugs of mercury.
Sixty-four pounds of mercury, to be exact. Enough to fill 30,000 thermometers.
His grandfather apparently had stored the jugs 13 years ago, when he was thinking about mining gold. Figuring he might make a few bucks, Winter, 23, posted a photo on Craigslist and offered the batch for $650 -- not realizing that mercury is a highly toxic metal subject to tight legal restrictions.
On Thursday, officials announced that a state hazardous waste specialist, acting on a tip from someone browsing the online site, went to Winter's home and picked up the mercury after the state Pollution Control Agency (PCA) paid $300 for it.
It was the largest amount of mercury that officials recall ever getting from one house, although large amounts sometimes are collected at industrial sites.
"Industry spends millions of dollars to cut back emissions of less mercury than we recovered here," said Jeff Connell, a PCA enforcement manager.
The action removed a hazard and saved Winter from unknowingly making an illegal sale to an unauthorized buyer.
"This material could have ended up in a dumpster from a person cleaning out a garage, so the mere fact that [Winter] bothered to take a picture and offered to sell it -- well, we're lucky," said Carl Herbrandson, a toxicologist with the Minnesota Department of Health. "This is dangerous stuff."