if something coal something else then that something is the sink of that something else
coal is naturally_occurring_tangible_substance. wood_coal is organic_matter. sink is tangible_thing. sink is not tangible_thing. wood_coal is not organic_matter. coal is organic_matter. coal_field is not unnatural_thing. coal_field is unnatural_thing. coal is not naturally_occurring_tangible_substance. coal is not organic_matter.