~70% of the world's phosphate reserves are in Morocco. Considering how important phosphates are to the entire planet's food security I'd rate it near the top of the list. Practically speaking, phosphates are a non-renewable resource.
And of course, phosphate reserves are only a small portion (0.02%) of the world's estimated phosphate resources.
Moreover, they are famously the limiting element in Isaac Asimov's thought-experiment of converting the earth's crust into biomass.