The nickel price is dropping sharply overnight to USD 15,400 at present, but the exchange rate is now at $1 AUD buys $0.82 USD and Sirius just announced the on switch for their mining operation.
I don't think a sudden fall in the nickel price will stop a re-rate in Sirius over the next few days. Now there is almost certainty that a mine will occur and the financing is on very favourable debt terms.
This news probably was missed by many due to the announcement late in the day. It is very significant in my opinion and management make it sound like it was regulation.