On an industrial park about an hour’s drive toward the South China Sea coast from Ho Chi Minh City sit giant mounds of raw metal shrouded in black tarpaulin. Stretching a kilometer in length, the much-coveted hoard could be worth about $5 billion at current prices.

In the esoteric world of aluminum, those in the know say the stockpile in Vietnam is the biggest they have ever seen — and that’s in an industry that spends a lot of time building stockpiles while analysts spend a lot of time trying to locate them. But as far as the increasingly under-supplied market is concerned, it’s one that may never be seen again.

Why it’s unlikely to move anytime soon involves Vietnam’s customs authorities. How its existence has become so significant, meanwhile, opens a window on a ubiquitous, yet erratic commodity at a time when makers of everything from car parts to beer cans are competing for more of it as they emerge from the COVID-19 pandemic and China throttles supply.