(1) Aggressive shorting, leading to...(2) Stops being hit...

(1) Aggressive shorting, leading to...
(2) Stops being hit causing more selling, leading to ...
(3) Margin calls being made on those with margin loans.

Typically margin calls are made after 2 pm, and the big fall at 2:30 pm I suspect was a large group of shares being sold all at once. Whether that was due to a margin call, a stop-loss, or another reason I don't know.

EXT is now valued at US$3.55 per lb, assuming a resource size of 427 Mlb. This is based upon analysis of drilling reports by EXT. The actual resource is likely to be larger as there is always a backlog of drill results to be assayed, collated and reported. Therefore the actual value is probably closer to US$3 per lb, or even less.

This is astonishingly cheap. It wouldn't surprise me if the share price bounced tomorrow.