copper price, page-59

Building a large term stockpile of crushed sulphide ore can also generate additional problems

depending on the sulphide minerals present, the storage conditions and the particle size, you may get problems with oxidation (can impact the recoveries) - this is why sulphide core for metallurgical test work is usually stored in an inert atmosphere and/or kept as cool as possible to ensure the sulphides stay 'fresh'

spontaneous combustion could also (very unlikely)be an issue.

just not a good idea to have large stockpiles of finely crushed sulphides sitting around for a period of time in a hot/wet oxidising environment.