The earth is constantly changing which means the conditions necessary to form different minerals change in regions everywhere. Tectonic, climactic, environmental. An area once covered by a sea has limestone deposited over millions of years. Tectonic action could form a volcano subjecting the limestone and other minerals to chemical, thermal and other environmental factors changing the conditions prevalent for eons. All have influence on the formation of minerals. The earth has been subjected to untold amounts of these changes. Doing the math, there exist many possibilities for similar developments in different places. So much so the mineral diversity is what it currently is.