Question about purification circuit, page-18

Yes, I believe you are right - the picture is not quite as simple as I paint in that last line.

The early ponds are designed for permanent impoundment of the halite salts. The harvest ponds will be designed anticipating sylvite recovery - this came up during the discussion of inventory in the conference call early this year. Part of the brine inventory issue was that brine is trapped in the porosity of the precipitated salts - this appears to have been significant in the harvest ponds

From the Seeking Alpha transcript of the call -
"The other aspect of inventory is that in the final ponds, the harvest ponds. Although, it’s a
recoverable inventory, it’s correct if I can put it that way in the graph, there is actually a
proportion of that that is not immediately recoverable. We recover it when we start mining that salt. It’s the only ponds where we actually you do recover the salt and we drain the salt and we get an ongoing process later on of recovering that inventory.

So you need to have a higher level of inventory in those harvest ponds than you would
have anticipated. So those areas are fully understood now, and the models are being
adjusted. And consequently, we can confidently say that we need to make these changes
in the inventory level. So increasing the inventory levels of higher grade material in those
harvest ponds, and reallocating through the system from the low grade ponds through the
intermediary ponds. And that’s the process we go through."

So the sylvite salts will be harvested and drained in due course, but in the absence of a potash circuit, they will not be further processed. I expect the drained salts could be stockpiled for later potash recovery.

And, anticipating a question about brine lost in the early ponds

"And in terms of the losses in the salt that you’re talking about, within the bulk of the ponds, that’s a permanent loss. So that’s taken into account in the calculation of recoverable inventory. So I want to make that clear. And in terms of the losses of brine within these final ponds, it’s a temporary loss because we mine the salt out later and drain as they do at Atacama."

They may be able to pump the brine from the salts in the early ponds before those ponds are permanently capped at end of life