Waste in the ponds produced by leaching gold from ore is a source of potential environmental dangers.
Gold is an ore.
The context holds that Gold is leached from the ore. We are to assume that we can only use information and knowledge presented by the context. The context given does not state that Gold is an ore, nor does it state that it is not an ore. Therefore the statement "Gold is an ore." can neither be definitely correct nor definitely incorrect when in connection with the information only found in this context.
( z1 ore :domain ( z2 gold ) )