Louisiana State Gemstone

Agate

(SiO2 )

Adopted in 1976

In 1976, Louisiana adopted petrified palmwood as the official state fossil, and agate, as found in Louisiana gravel, became the state gemstone.

Louisiana Legislature Archives
§163.  State gemstone
There shall be an official state gemstone.  The official state gemstone shall be the agate, as found in Louisiana gravel.  Its use on official documents of the state and with the insignia of the state is hereby authorized.

Added by Acts 1976, No. 362, §1.

It is a variety of translucent microcrystalline quartz called "chalcedony," which is characterized by well-defined banding. This might be confusing, because scientifically agate is considered a variety of the mineral quartz. Minerals are the building blocks of rocks. Agate is considered both a mineral (cryptocrystalline quartz) and a rock, and is formed by chemical precipitation from silica-rich solution in rock cavities. Agates are found within the Citronelle Formation and younger sediments in the Feliciana Parishes. Both the agate and chert originally formed within limestone that covered the central United States. Erosion released the state's gemstone from these limestones, and ancient rivers carried them into Louisiana and Mississippi.

Did you know that one of the best collecting localities for the state mineral (agate) is located close to Baton Rouge? The gravel beds along the Amite River are the primary collecting locality for the Louisiana Geological Survey.