Tennessee river pearls were designated the state gem of Tennessee in 1979. River pearls are created by mussels and are found in all colors and various shapes (spherical, pear-shaped, and irregular). Tennessee river pearls are among the most beautiful and durable in the world.

After World War I, dams were built on many Tennessee rivers and the mussels lost their swift and shallow shoals. The waters also became more toxic. Tennessee river pearls are collected and crafted into rings, cuff links, stick pins, and other jewelry.

Source:

Tennessee Symbols: Tennessee Blue Book (PDF)
River pearl photos from www.TennesseeRiverPearls.com are used by permission.

Links:

Geological Symbols - 50 States List