Importantly, the growth comes mainly from the Greens Creek and Casa Berardi mines, which generate about 85% of the company's revenue.

As at December 31, the Coeur d'Alene, Idaho-based company reported record proven and probable gold reserves of 2.85Moz, an increase of 26% from 2017.

Hecla said silver proven and probable reserves also rose 8% year-on-year to 191Moz, while lead proven and probable reserves were at a record 774,000 short tons, an increase of 5%. Zinc reserves of 931,730t reflected an increase of 11% and were the highest since 2009, the company said.

Hecla used price assumptions for its reserve calculations of $1,200/oz gold, $14.50/oz for silver, $1.15/lb zinc and 90c/lb for lead.

"We have achieved this while the industry has generally seen declining reserves and we were able to use among the most conservative price assumptions in the industry because of the strong economics of these deposits," CEO Phillips Baker Jr said.

The company expects 2019 to be another big exploration year. Baker said the focus would be on San Sebastian, Casa Berardi and Nevada, of which Nevada was expected to take about half of the exploration budget.

Hecla has gained nearly 11% since the start of the year in New York, which helps offset a 12-month decline of a third of its value. The company closed 1.18% higher Thursday at $2.58, adding another 7c in after-market trading. The company is capitalised at $1.24 billion.