Prospecting is an initial upgrade which allows miners to produce/obtain ores, a basic resource. To unlock it, 10 ore is needed, which can be obtained by clicking the 'Mine Stone' button. Once unlocked, the upgrade takes place automatically.

Initial SkinningHarvestingProspectingMasonry
Masonry DomesticationPloughsharesIrrigation  –  ConstructionGranariesBasic WeaponryBasic Shields  –  Horseback RidingThe Wheel  –  Writing
Construction ButcheringGardeningExtraction  –  Architecture  –  TenementsPalisade
Architecture FlensingMacerating  –  Crop RotationSelective BreedingFertilisers  –  Slums  –  Civil Service  –  Start Building Wonder
Writing AdministrationCode of LawsMathematicsAesthetics
Civil Service FeudalismGuildsSerfsNationalism
Trade TradeCurrencyCommerce