Ann: Quarterly Report - December 2018, page-66

Just a little bit of perspective.
If we assume the cash margin will be the same for CY2019 (i.e. US$288/t) and the production is the lower end of forward guidance (180,000 - 210,000 t), Mt Cattlin will earn:
288 x 180,000 = US$51.84m operating margin for CY19.
Translate that to a valuation, and Mt Cattlin on its own operating at the lowest end of expectation is still worth US$518.4m (or A$725m).
I don't think the sell off will last too long.