INL Chart, page-74

It would seem from the following comment re zinc pricing that the company should be able to negotiate a favourable deal for their zinc asset

"One of the reasons behind the rally in zinc is capacity coming out of the market through mine closures – these include Century (~450,000tpa Zn in concentrate) and Lisheen (~165,000tpa Zn in concentrate) – this is ~4% of global supply, on top of Glencore in late 2015 also reducing production by ~500,000tpa in response to falling prices.
The zinc supply crunch is therefore very real and after almost a decade of false hope, it’s arrived. We’re seeing closure after closure in the zinc mining space as aging mines reach the end of their useful lives. At the same time, there has been relatively little spent on exploration and development of new mines over the past decade, meaning higher prices are a reality. There’s a very strong window of opportunity for investors and companies that can bring new operations on stream over the next few years. With the exception of Glencore, many of the majors don’t have much exposure to zinc
What of the future? Our view is that the key drivers for zinc prices will include restarts of any of Glencore’s operations and China’s steel production rate – China is the largest consumer and a net importer of zinc, consuming some 46% of global mine supply of ~13.4Mt in 2014. There is no new production on the horizon outside of China, and thus we would expect zinc prices to remain relatively strong in the medium to long term, trading in the range of US$2,200 – US$2,400 per tonne, although short term prices may be considerably higher – given the recent price history this view may actually be conservative".