Lime or Volcanic Ash as a resource?

I'd like a random event to reveal Guano, which somehow helps with agriculture.
 
Lime and ash would be represented as stone. I would love to see Tea, Salt, and maybe even Cotton, Tobacco, Olives, some sort of cash crop other than tobacco (indigo?), and Coffee added. Salt is extremely important, and most of the other ones are luxury resources which Europeans set out to find because they were addicted, which started their colonization of the world.
 
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