Freshwater pearl earrings; photo by Alejandra Quiroz on Flickr (noncommercial use permitted with attribution / share alike).
Official State Gemstone of Kentucky
Kentucky designated freshwater pearl as the official state gemstone in 1986 (the "river pearl" is also a state symbol of Tennessee). All State Gems & Gemstones
Freshwater pearls are found in the Tennessee River Valley and the Mississippi River Valley of Kentucky. These unique gemstones are created by freshwater mussels (bivalve mollusks).