Heap leaching is a process used to recover minerals from low-grade ore, involving the use of a solution that dissolves the minerals. The process involves laying down an impermeable leach pad, heaping ore on the pad, and then using a drip system to spread a leach solution over the ore. The minerals dissolve into the leach solution, which is recovered and separated out in a processing plant. The entire process can take from several months to several years, but is considered quite economical.
An inventory asset can be recognized through the use of assay testing and physical measurements to determine the quantity of minerals on a leach pad, also factoring in the proportion of expected metal recovery.