Mineral material which is not rich enough in metal to be economically viable as ore, but which has enough metal that in future it may be considered ore-bearing, either because
- future improvements in technology make extraction of it profitable; or
- natural processes such as secondary enrichment (further leaching by groundwater) may cause separation of the protore into more concentrated ore and its residue; or
- market value of the material makes it worthwhile using existing technology to try to extract more of the ore from it.