See slides 13 and 45. GORO has a 3.6% Zinc by-product P&P grade which contributed US$ 26M in 2016 revenue as a by-product credit help keep GORO's cash costs/AISC down. By my posts for last year I'm bullish on zinc for next couple years and so are others so this is a nice tailwind that should keep GORO's costs down. You can quickly calculate from slide 13 that based on 14,302 tonnes of zinc production GORO received US$ 1800/tonne in 2016 and prices currently around US$ 2500 tonne. Assume a similar level of production and US$ 2500 flat pricing for 2017 and there is an instant US$ 10 million increase in revenues over last year (or decrease to cash costs/AISC depending on your approach)
To come from the contrarian point of view - if GORO ever runs out of 3.6% zinc then sell as costs are going to jump materially. This probably isn't a risk but going to go email company now.