Gator Girl Rocks

Rockhounding Louisiana

Louisiana is a good state for rockhounding.  Louisiana is well known for oil and gas as well as salt domes.  The state, however, also has some rockhounding opportunities.  In addition to a variety of fossils, Louisiana has abundant agate, chert, and petrified wood.

 

State Rocks, Gemstones, Minerals, Fossils, & Dinosaurs

Rockhounding Tip:  Knowing state rocks, gemstones, minerals, fossils, and dinosaurs often can be very useful information for rockhounders.  Ordinarily, states with significant mineral deposits, valuable gemstones, fossils, or unusual or significant rock occurrences will designate an official state mineral, rock/stone, gemstone, fossil, or dinosaur to promote interest in the state’s natural resources, history, tourism, etc.  Accordingly, such state symbols often are a valuable clue as to potential worthwhile rockhounding opportunities.


State Gemstone:  Cabochon Cut Oyster Shell (2011)

Louisiana designated the cabochon cut gemstone derived from a special Louisiana-grown oyster (the Crassostrea virginica mollusk) as its official state gemstone in 2011 (the cut and fashioned shells are considered to be a gem).  The oyster shell gemstone can be fashioned from a species of mollusk that is bountiful off the Louisiana coast.  Note:  Between 1976 and 2011, Louisiana had designated agate - as found in Louisiana gravels - as its official state gemstone.

 

State Mineral:  Agate (2011)

Louisiana designated the agate - as found in Louisiana gravels - as its official state mineral in 2011.  Between 1976 and 2011, Louisiana had designated agate - as found in Louisiana gravels - as its official state gemstone.  Agates are found within the Citronelle Formation and younger sediments in the Feliciana Parishes.  The agates found in Louisiana likely formed within limestone sediments of the upper Midwest.  The agates eroded out and were transported down ancient rivers to Louisiana where they now are found in gravel beds.

 

State Fossil:  Petrified Palm Wood (1976)

Louisiana designated petrified palm wood as its official state fossil.  Petrified palm wood includes a group of fossil woods that contain prominent rod-like structures within the regular grain of the silicified wood.  Depending upon the angle at which they are cut by fracture, these rod-like structures show up as spots, tapering rods, or continuous lines.  These rod-like structures are sclerenchyma bundles that give the palm tree its vertical strength.  In Louisiana, most of the petrified palm wood belongs to the genera Palmoxylon.  The petrified palm wood in Louisiana is the petrified remains of trees that grew on the Gulf Coastal Plain during the Oligocene Epoch, around 30 million years ago.  At that time the shore of the Gulf of Mexico was further north than it is now, which explains why the wood is usually found in the more northern parishes of the state, frequently in the Catahoula Formation of sedimentary rock that stretches from Louisiana into Texas and Mississippi.
 The petrified wood formed when a tree died and was buried by sediments.  Minerals in the groundwater permeated the wood, replacing the original organic matter and turning the wood to stone.  The main mineral is silica, but trace elements in the silica impart a variety of colors to the petrified wood.  Artifacts made of petrified wood found at Paleo-Indian sites indicate that Native Americans have known of these deposits for thousands of years.  In Louisiana, petrified palm wood is found in the parishes of Rapides, Natchitoches, Grant, and Sabine.

Rockhounding Resources

Louisiana Geological Survey
The Louisiana Geological Survey is the premier geological research institution in the state of Louisiana.

 

• Darwin Spearing, Roadside Geology of Louisiana (2007).
• June Culp Zeitner, Southwest Mineral & Gem Trails (1972).
• Allan W. Eckert, Earth Treasures Vol. 4A - Southwestern Quadrant (1987; reprint in 2000).
• James Martin Monaco & Jeannette Hathway Monaco, Fee Mining & Mineral Adventures in the Eastern U.S. (2d ed. 2010).
• Kathy J. Rygle & Stephen F. Pedersen, Southeast Treasure Hunter's Gem & Mineral Guide (4th ed. 2008).

 

Museums of Interest to Rockhounders

International Petroleum Museum & Exposition
Morgan City, Louisiana
The International Petroleum Museum and Exposition is a non-profit corporation established for the purpose of educating the general public, and the next generation, on the significance of the offshore oil and gas industry and its affect on the local area, the state, the nation, and the world.

Louisiana Museum of Natural History
Louisiana State University – Baton Rouge, Louisiana
LSU’s Museum of Natural Science’s exhibit area is located in Foster Hall.  Exhibits include mineralogy and petrology.

 

Lafayette Science Museum
Lafayette, Louisiana
The museum has a small collection of fossils, meteorites, and tektites.

Places to Visit - Interesting Sites To See

Brushy Creek Impact Crater
South of Greensburg, Louisiana
A few miles south of Greensburg, there is a noticeable dip in Louisiana Highway 37.  LSU scientists working for the Louisiana Geological Survey determined that the site is an historic meteor crater that likely occurred 12,000 to 10,000 years ago.

Rockhounding Sites for Children & Families

Petrified Palm Wood
Toledo Bend Area – Border between Louisiana & Texas
In Louisiana, petrified palm wood is found in the parishes of Rapides, Natchitoches, Grant, and Sabine.  The Toledo Bend area has occurrences.  Petrified palm wood also occurs in east Texas.

Agate
Baton Rouge, Louisiana
Agate occurs in the gravel beds along the Amite River near Baton Rouge.  Often times, the agates will display banding.

Agatized Coral
Southern Louisiana
Agatized coral occurs in current and historic stream gravels.  Accordingly, agatized coral may be found in gravel operations (my dad found one for me in an over-size pile of gravel from a dredging operation outside of New Orleans).