In the last 7 trading sessions, commodity stocks have been in a free-fall. Look at what has happened to these big names, most of which hit historic highs in June or July:
Nucor: 52-week low on heavy volume (55% off high)
Potash: 6 month low on heavy volume (41% from historic high)
Freeport-McMoran: 52-week low on heavy volume (47% from historic high)
Valero: 3 year low on heavy volume, (59% from historic high)
Massey Energy: 5 month low on heavy volume (56% from historic high)
This is more than just normal trading, there is clearly margin calls of some sort going on that is leading to liquidation of positions. Aside from the uncertainties in financials, answering the question, "When does the commodity stock selloff end?" is the most important question on the Street.