The Toronto-headquartered producer outlined a probable reserve at ELD of 86,000oz gold in 487,000 tonnes at an average grade of 5.5g/t. The company used a cut-off grade of 3.7g/t.

The reserve is a subset of an indicated resource of 141,000oz held in 797,000t grading 5.52g/t, using a 2.5 g/t cut-off grade.

"This addition of the ELD mineral reserves, while small in comparison to the openpit mineral reserves, provides a nice sweetener to the openpit production," said CEO Fred Stanford.

"It is also indicative of the potential to add further underground mineral resources. With ELD open in three directions, the Sub-Sill underground deposit still open at depth, and the potential for down dip extensions of Guajes, we are upbeat about the potential to further expand underground reserves and resources through multiple sources."

Torex said it planned to use the Muckahi mining system to exploit the deposit, since it could potentially achieve lower-than-conventional mining costs. This also raises the possibility of lowering the cut-off grade and increasing the size of the mineral reserve.

The company is now busy excavating a 30-degree down-ramp to access the lower parts of the ELD deposit. In the upper portions of the deposit the excavations are nearly complete for initial long-hole stoping.

The El Limon-Guajes openpits are north of the Balsas river and constitute some of the best openpit gold deposits at a reserve grade of 2.7g/t. They are among the largest and lowest-cost gold mines in the world.

The complex, which includes ELG and the Sub-Sill, is expected to produce 2.7Moz/y gold through 2023 at an average all-in sustaining cost of US$734/oz.

Torex (TSX:TXG) gained C31c or 2.23% on Thursday in Toronto to close at $14.21. It has a market capitalisation of $1.21 billion.