The run of mine (ROM) ore refers to ore in its natural, unprocessed state just as it is when blasted.
Clearly, the above explanation leaves out many details to enable us to understand as to why we as resource investors should care about the ROM so just consider the following fact: every time ore has been extracted from the earth, the metal or other valuable materials it contains must be recovered via “processing”. The first stage in processing ore involves crushing and grinding the rock to the point where it becomes a fine sand-like substance so that commercially valuable minerals or metals can be separated from the waste material.
Now—and this is the important part—as far as processing is concerned, size does matter: grinding costs more than crushing, and the smaller the crush size, the more it costs. So the less crushing you need (the larger the chunks of rock), the less energy for processing your operation will consume. Cheapest of all is if you have ore that shatters on its own when you blast it in your open pit (or is a sand or clay that can simply be scooped up) and can be placed on the pad to be heap-leached; a process, whereby a solution is sprinkled to percolate down through the heap of ore dissolving the mineralization contained in it (see heap leaching).
This is exactly what miners refer to as the “run of mine” ore and it’s the cheapest rock to process; so much so, in fact, that it may even offset slightly lower metal recovery rates, if it saves your company the cost of building and operating all those pricey crushing plants that is.