Presented with nothing but admiration for the arrogance of manipulators.
Because nothing says fiduciary duty or best-execution like a 2-second dump of 1.25 million shares of Gold Miners (driving prices down $2)
Sell Mortimer Sell...
and close-up thanks to Nanex... a perfect dump to the LULD circuit breaker levels!!!!
Just like AAPL, when it hit the lower bound on its LULD:
So that's it - how to trade US equity markets, trail bids 10% below every tick and offers 10% above (or whatever the circuit-breaker LULD barriers are in your market - and hey presto, instant money.
As for what caused it, nobody knows, or will know: a market may be broken but as long as it keeps going up, nobody cares (when it all goes to hell, that will be a different story but everyone at the SEC will conveniently have resigned by then). One theory, is that like earlier today when a bunch of stocks went ballistic on an ETF trade, is that the DUST gold miner 3X ETF went vertical for whatever reason, and in turn it send the gold minger space plunging.
A theory, but as we noted: nobody will know, because frankly, nobody even cares any more.