A 261,000-ton stockpile of arsenic dust kept frozen in chambers up to 250 feet down at the edge of Yellowknife has given researchers a sample they turned into arsenic metal more than 99 percent pure,

There's a decent chance the phone in your pocket has a little arsenic in it. Gallium arsenide handles radio duties in plenty of electronics, arsenic turns up in some solar tech and batteries, and metallic arsenic now sits on critical mineral lists in several countries, the US included. So here's a question I didn't expect to be typing this week: what if one of the best untapped sources of a critical mineral is arguably the nastiest pile of mine waste in Canada? That pile sits under Giant Mine, a closed gold mine on the edge of Yellowknife in the Northwest Territories. The mine's roasters left behind 261,000 short tons (237,000 metric tons) of arsenic trioxide dust, and the Canadian Light Source says that's enough to fill seven 10-story buildings or 9,480 dump trucks. Canada's answer so far has been to keep the dust frozen underground.