Manufacturing

Miami oolite, or Miami limestone

Miami does not have a big manufacturing core like the East Coast and Central United States, but that is not to say no important natural resources exist in Miami.  Miami's bedrock is made of all Miami limestone.  The limestone was a result of the change in sea level starting about 130,000 years ago.  About 4,00 years ago when the sea level had stabilized the limestone and a thin layer of soil were just above sea level creating the Southeast portion of Florida.  besides the limestone Miami is also has a very important underground aquifer that provides fresh water for the Miami-Dade county.  The Biscayner aquifer runs from Palm Beach county to the Florida Bay. (source) 

A total of 6.1% of Miami's working population work in either mining or manufacturing.  Most of Miami's jobs are in offices or in shipping.

http://www.miamidade.gov/planzone/library/narratives/EmploymentGlance.pdf