The FTSE 100-listed company said it was on track to meet its full-year guidance of 700,000 tonnes, after posting a 5.5 per cent increase in second-quarter copper output to 178,800 tonnes.
This was not good enough for the market, however, as the consensus was for Antofagasta to beat its full-year guidance.
The company had ramped up production in the second quarter, after maintenance work hindered first-quarter output.
The company’s cash costs were in line with the previous quarter and full-year guidance at $1.45 (86p) per pound, due to increased returns from by-products at the Los Pelambres mine.
“A reasonable result with by-product credits at Los Pelambres offsetting some moderate underperformance at other assets,” said Investec research.
“The company continues to look expensive, but offers the closest correlation to copper prices of UK miners.”
The company said that the construction of the Antucoya mine remains on time and on budget, with 86 per cent of the project completed as of 30 June.
Like the rest of the sector, Antofagasta has been struggling to grow its bottom line due to weak commodity prices, as a result of slowed growth from China.
In March, it revealed a 30.1 per cent fall in full-year earnings to $2.7bn, with record copper production offset by the lower metal prices and higher costs.
Shares closed 4.6 per cent lower at 816p.