Alabama

 

Geological State Symbols Across America           Geology of the National Parks Through Pictures


Alabama State Geological Symbols
Type
Symbol
Year Established

State Rock

Marble
1969
State Mineral
Hematite
1967
State Gemstone
Star Blue Quartz
1990
State Fossil
Basilosaurus cetoides
1984

 

State Rock: Marble


Sylacauga Marble

Book covering the history of the Sylacauga marble. (sylacauga.net)

Marble is a metamorphosed variety of the sedimentary rock limestone. This means that the original sedimentary rock underwent periods of increased temperatures and pressures to change the rock itself. The primary minerals in marble are calcite (CaCO3) or dolomite ((Ca,Mg)CO3) but it will usually have other mineral contaminates mixed in as well (i.e., clay, mica, quartz, pyrite, and iron oxide, etc.). Since, the primary mineral in marble is calcite, most marbles will have a white color with swirls of darker colors (the contaminates) but marbles can be found in many different colors depending on what impurities were present in the initial limestone. During metamorphism of the original limestone, the calcite is recrystallized to form interlocking crystals, which will usually destroy any remnants of the original rock, including any fossils present.

 

Marble Sculptors

Sculpting the Sylacauga Marble during the Magic of Marble Festival in 2010. (sylacauga.net)

The primary source of marble in Alabama is the Sylacauga marble found in Talladega County. The Sylacauga, or Alabama, Marble has been quarried and used in art and building stones throughout Alabama and the US. The marble is named for the town Sylacauga and has been called the "whitest marble in the world" for its purity. The Sylacauga Marble has been used in several famous landmarks including the Washington Monument, the Lincoln Memorial, and the U.S. Supreme Court. The marble formed during metamorphism associated with the Appalachian orogen (mountain building) and is approximately Cambrian to Ordovician in age. Besides the pure white sections of the marble, there are also sections that have green, pink, gray, black, and gold veins in the ~5.5 cubic mile deposit. Official descriptions of the marble state it as "white and pale-blue to light-gray calcite marble, locally containing interlayered dolomite marble and thin phyllite layers" (mrdata.usgs.gov).


State Mineral: Hematite


Hematite varieties

Images of red and silver hematite (geology.com).

Hematite is a mineral that is produced from the oxidation of iron, and forms iron oxide in the form of Fe2O3. In everyday language, this means that hematite is more commonly known as rust. Hematite is primarily composed of iron and is abundant on the Earth's surface,resulting in hematite becoming one of our most common sources of iron ore. Although typically found as a red "earthy" deposit, there is also a variety of hematite that has a silver/steel-grey metallic appearance to it (pictured left). Both varieties of hematite can be easily identified by the characteristic bright red streak of the mineral. Hematite has a hardness of 5 to 6, meaning that it is approximately as hard as a plane of glass (5.5). The mineral hematite was originally named "aematitis lithos" in ~300 BCE by the Greek Theophrastus and its name means "blood stone". The name was translated by Pliny the Elder to haematites, meaning "bloodlike", and that name eventually evolved to the modern spelling of "hematite".

 

Statue of Vulcan

Cast iron statue of Vulcan from Birmingham, AL (wikipedia.com).

The hematite in Alabama was primarily mined from the Red Mountain Formation until 1975, where it became cheaper to import it. At one time it was Alabama's most developed, non-fuel, mineral industry, helping to build up Birmingham as an industrial center. In the 135 years hematite was mined, ~375 million tons of ore was excavated. The Red Mountain Formation is primarily a Silurian interbedded shale-sandstone with some siltstone and limestone deposits intermixed. The hematite is largely from cross-bedded sandstone members of the Red Mountain Formation, which were deposited as shoreface (essentially beach) deposits. The production of hematite within the sandstone was precipitated during periods of sediment starvation and reworking during a regression (sea-level drop). Birmingham is also known for the largest cast-iron structure ever made, the statue of Vulcan (picture right), produced entirely with the Birmingham iron ore.


State Gemstone: Star Blue Quartz


Star Blue Quartz

Star blue quartz (Alabama.gov).

Quartz is one of the most common minerals on Earth, primarily due to its simple structure and chemical formula, SiO2. Quartz also has an extremely high hardness, 7 on Mohs hardness scale, meaning that it doesn't scratch very easily and therefore does not break down easily. As the rocks on Earth are slowly eroded over time, most of the other minerals will break down into clay while quartz grains will generally just gets smaller and smaller. The result is that most beach sand is composed of quartz that has a slight hematite (rust) stain to it to give the sand grains their slight yellowish color. Although quartz is a simple mineral, it can come in a variety of colors depending on what type of impurities are present in the crystal structure; pure quartz crystal is clear, milky quartz is white, smoky quartz is grey, amethyst is purple quartz, citrine is yellow quartz, rose quartz is pink, as well as some other colors and varieties. Quartz does not have any cleavage, meaning that when it breaks it doesn't form along perfect surfaces. Instead as the quartz crystals grow, individual mineral molecules of quartz are added to the outside of the crystal from water rich in dissolved SiO2 or mineral melt (liquid rock like lava or magma).

 

Unlike the other varieties of quartz (such as citrine or amethyst), pure blue quartz has not yet been found in nature. Instead, the quartz crystals appear blue because of the inclusions of other minerals or properties of the mineral itself that make the light reflect through the mineral and makes it appear blue. The reason that Star Blue Quartz is blue is that it contains little bits of amphibole (another type of mineral) and displays asterism (a star pattern in the light) when polished. The problem with this variety of quartz though is that there is little to no information on where to find it or why it was even listed as the state gemstone. The best that I can find is the constantly rehashed phrase from when it was promoted to the state: "(star blue quartz) is one of the most beautiful gemstones on earth, and the cheapest because there are so many." It appears that this very common mineral is rare to non-existent in Alabama. There have been reports of it along the Flint River, but most of those occurrences are generally in neighboring Georgia.


State Fossil: Basilosaurus cetoides

 

Basilosaurus

Basilosaurus skeleton from the National Museum of Natural History (Wikimedia.org).

 

Basilosaurus is a member of the whale family (Cetacea) first discovered in Alabama in 1834. It was originally thought to be a swimming reptile but was later discovered that it was indeed a whale from the Eocene period (40-35 million years ago). Unlike modern day whales, Basilosaurus still retained its hind limbs. These were thought to be mostly nonfunctional, however there is a theory that they could have been used during sex. Basilosaurus is one of the closest related animals to modern day cetaceans (dolphins, whales, etc.) that still retains their hind-limbs, although the pelvis is not connected to the vertebrae, limiting any function that it could provide.

 

Basilosaurus lineage

Phylogenetic relationships of early cetaceans (from Houssaye et al., 2015).

 

The group Basilosauridae contained a few other species that had body proportions similar to modern day dolphins but Basilosaurus had an "exceptionally long body and tail" resulting in the animal having a more snake-like appearance. The body length ranged from 49 to 59 ft and is one of the largest known animals during the Paleocene-Eocene time period. Basilosaurus is most abundant in Alabama and has been found in Clarke, Choctaw, and Washington counties.

 

References

https://statesymbolsusa.org/states/united-states/alabama
http://www.sylacauga.net/library/sections/Sylacauga%20Marble%20Fiestival/Marble%20Fiestival%202010.htm
http://en.wikipedia.org/wiki/Vulcan_statue
http://geology.about.com/od/regional_geology/ig/stategems/stateblueqtz.htm
http://www.encyclopediaofalabama.org/face/Multimedia.jsp?id=m-3931

http://legacy.decaturdaily.com/decaturdaily/news/050206/marble.shtml

https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=ALsgq%3B7

http://geology.com/rocks/marble.shtml

https://www.mindat.org/min-1856.html

https://geology.com/minerals/hematite.shtml

https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=ALSrm%3B3

https://en.wikipedia.org/wiki/Basilosaurus

Chowns, Tim & Rindsberg, Andrew. (2015). Stratigraphy and depositional environments in the Silurian Red Mountain Formation of the southern Appalachian basin. 10.1130/2015.0039(04).

Houssaye A, Tafforeau P, de Muizon C, Gingerich PD. Transition of Eocene whales from land to sea: evidence from bone microstructure. PLoS One. 2015;10(2):e0118409. Published 2015 Feb 25. doi:10.1371/journal.pone.0118409


Geology of Alabama's National Parks

Through Pictures

(at least the one's I have been to)

 

Russell Cave National Monument

During a trip to Chattanooga for my wife's Ironman race, we took a tour of some of the nearby National Parks. This included a brief foray into Alabama to see the small, but cool Russell Cave.

Russell Cave NM

Entrance Sign

 

Russell Cave NM

Within the museum and visitor's center there are several panels of artifacts explaining about the Native People who used to live in the caves and how geology was related to their lives. Here the first farmers are mentioned who used nearby flint (a silica/quartz based rock that is very hard and can be broken to have very thin and sharp edges) and limestone (the rock the caves were formed within) as materials to make tools.  

 

Russell Cave NM

More use of geology, this time for of weapons and more tools. These were also used from nearby flint deposits.

 

Russell Cave NM

Here are the remains of many of the animals found within the caves that the Native People used for food.

 

Russell Cave NM

Here is the main mouth of Russell Cave as you walk up to it from the trail. The entrance has a very large cave mouth and was primarily the place where the Native People resided. Despite Russell Cave being the 19th longest cave in the US, most to nearly all of the activity was at the mouth.

 

Russell Cave NM

Here is another shot of the cave right before going in.

 

Russell Cave NM

View from the edge of the cave. Most caves are formed by the dissolution of limestone from running water. In this instance the creek is visible in the previous photo which caused the dissolution. The limestone here can be broken up into three different rock units: the Monteagle Limestone, the Bangor Limestone, and the Pennington Formation. All of these units are Mississippian in age (over 300 million years old). The overlying rock is a sandstone. The overlying rock is a very important part of cave formation because without a sturdy roof rock that resists fracturing, the dissolution of the cave would just cause the entire ground to collapse and no cave could be form. The sandstone is younger than the limestone (hence it being on top) and is Pennsylvanian in age and called the Pottsville Formation (npshistory.com)

 

Russell Cave NM

This sign within the cave explains that cave roof collapses made it possible for people to live within the cave, causing the floor of the cave to rise above flood waters. The cave was inhabited from about 11,000 years ago to 9,000 years ago.

 

Russell Cave NM

A couple of hundred feet away from the main entrance is this sinkhole that you can see within the forested area. Here the cave roof, the sandstone, was not strong enough to hold itself up over the dissolved rock and collapsed into the hole below.

 

Russell Cave NM

Now this is an interesting rock that was just outside the visitor's center. The park service people placed it here on purpose right near a sign explaining it. It is a rock filled with these features called septarian concretions. Concretions are blocks of rock that form from the continued precipitation of minerals along the outer surface of the rock. They often form from hard minerals in softer rocks (such as calcite in a shale) and then when the softer rocks erode away, it leaves behind the concretion. Septarian concretions form in a similar manner, except that they have periods of contractions and expansions which produced cracks or stress fractures within the concretions themselves. These fractures will also fill with the precipitated minerals, producing these banded concretions of different minerals. As these minerals erode, they will erode at different rates all in relation to the hardness of the mineral being eroded producing this onion effect in the rock.