The DeGrussa mine produced 17,867 tonnes of copper and 9548 ounces of gold at C1 costs of US80c per pound.
The full-year result was 64,918t of copper and 39,273oz of gold at 93c/lb of copper, allowing the company to meet guidance of 63,000-66,000t of copper and 38,000-40,000oz of gold at 95c-$1.05/lb.
"It was pretty much the best quarter this company has ever had," Simich said on a conference call.
"It's extraordinarily pleasing to see at the end of our sixth year of operations.
"If you look at the prognosis for the next few years, it gets stronger and stronger and better and better."
Guidance for the 2019 financial year was set at 63,000-67,000t of copper and 37,000-40,000oz of gold at C1 costs of US$1-1.05/lb.
The outlook was below most analyst estimates, but the company noted the new Monty mine wouldn't come online until the end of the year.
Simich denied "totally and utterly erroneous" gossip that the company was considering conducting a rights issue.
"Sandfire is not considering a rights issue and is extraordinarily well-funded," he said.
"If you look at our financial results coming out next month, they will be the best we've ever had."
Sandfire closed the June quarter with A$243 million cash.
However, Sandfire's 78%-owned Toronto-listed subsidiary Sandfire Resources America will likely conduct a "modest" rights issue, in which Sandfire will participate.
It comes as Sandfire America's Black Butte project in Montana awaits a record of decision - much like a mining permit - in early 2019.
Simich said construction could begin shortly after.
On the business development front, Sandfire acquired a stake in Adriatic Resources during the quarter.
"We're very excited for Adriatic," Simich said, describing recent drilling from the Rupice project in Bosnia and Herzegovina as extraordinary.
Since the end of the quarter, the company has also bought a stake in Alaska explorer White Rock Minerals.
Simich said smaller-scale deals was about "putting bets on" and building the portfolio to potentially take full ownership if the opportunities developed down the line.
Aggressive exploration will continue across the 6276sq.km Greater Doolgunna project, including the Morck's Well discovery.
While intersections at the Auris Minerals-owned project have been narrow to date, the grades warrant further work.
Simich said the company would be aiming for a 50,000t copper resource there.
"It needs to be that sort of scale at relevant grades to be worth getting in the middle of," he said.
Shares in Sandfire dropped by 4.5% to $8.50, valuing the company at $1.35 billion.