The Geology P.A.G.E.: Geological State Symbols Across America

The next state up for the Geological State Symbols Across America is:

Arizona

You can find any of the other states geological symbols on my website here: Dinojim.com (being updated as I go along this year).

Year Established
State Gemstone: Turquoise 1974
State Fossil: Petrified Wood (Araucarioxylon arizonicum) 1988
State Metal: Copper 2015

I also have several Geology of the National Parks Through Pictures that I have done for Arizona previously. These include:
Canyon de Chelly National Monument
Casa Grande Ruins National Monument
Glen Canyon National Recreation Area
Grand Canyon National Park
Hohokam Pima National Monument
Petrified Forest National Park
Saguaro National Park
Sunset Crater Volcano National Monument
Tonto National Monument
Tumacácori National Historical Park
Walnut Canyon National Monument
Wupatki National Monument

State Gemstone: Turquoise

CHAPTER 55

House Bill 2109

AN ACT

RELATING TO STATE GOVERNMENT; PROVIDING THAT TURQUOISE BE THE STATE GEMSTONE, AND AMENDING TITLE 41, CHAPTER 4.1, ARTICLE 5, ARIZONA REVISED STATUTES, BY ADDING A NEW SECTION 41-858.
Be it enacted by the Legislature of the State of Arizona:
Section 1. Title 41, chapter 4.1, article 5, Arizona Revised Statutes, is amended by adding a new section 41-858, to read:
41-858. State gemstone·
TURQUOISE IS THE OFFICIAL STATE GEMSTONE.

A piece of turquoise from Madagascar.
Image courtesy of carionmineraux.com.

Turquoise is a blue-green mineral made up of copper, aluminum, and hydrous phosphate (CuAl6(PO4)4(OH)). The name turquoise comes from the French expression for "Turkish Stone", illustrating that the early sources for European turquoise were from the Middle East. Turquoise has long been considered valuable and is one of the oldest known gemstones. It has been found in ancient Egyptian and Chinese archeological expeditions, showing that those people used turquoise as far back as 3,000 years ago. It is formed by the flowing of groundwater through copper deposits that eventually react with phosphate and aluminum minerals. Turquoise is also only found in arid (desert) environments because that is one of the few places that allows the groundwater to maintain a high enough copper concentration for long enough to interact with the other minerals. The result is a gemstone unlike traditional, gemstones like ruby or emerald, which is most commonly opaque. The opaqueness is due to the structure of turquoise, which is made up of many microcrystalline structures instead of one large mineral crystal. These microcrystals give the turquoise its appearance, either a mottled look or a smooth finish, which is due to the size of these microcrystals. It is also extremely soft and easy to carve. All of these attributes make it useful for many different purposes from jewelry to architectural adornments.

Spiderweb turqouise jewlery.
Image courtesy of Durango Silver.

Turquoise mines can be found all across the southwestern United States, with the largest concentration found in Arizona. As mentioned above, turquoise mines in Arizona are often associated with copper mines (many of them open-pit mines in AZ). The largest and most well known of the turquoise mines is the Bisbee Mine, near Bisbee, AZ, located adjacent to the Copper Queen copper mine. In 1880, the mine was founded as a gold, silver, and copper mine, which are often found together due to the formation of these minerals from the waters associated with subduction zone magmatism. The hydrothermal waters associated with the former subduction zone in the region circulated throughout the rocks depositing the heavy metal deposits within the bedrock. These heavy metal deposits eventually interacted with the local groundwater producing these turquoise deposits. The Bisbee Mine turquoise was discovered in the 1950's and quickly became prized for it's spider-webbing patterns throughout the turquoise stones (pictured left). Although most of the turquoise has been mined out, this has resulted in these variety of the gem to become prized collectors items. Native Americans (primarily the Anasazi and the Hohokam) mined the turquoise in Arizona for use in jewelry and for trade. Arizona is also home to one of the largest domestic turquoise mines, located in Kingman.

State Fossil: Petrified Wood (Araucarioxylon arizonicum)

CHAPTER 88

SENATE BILL 1455

AN ACT

RELATING TO STATE GOVERNMENT; PROVIDING FOR ADOPTION OF PETRIFIED WOOD AS THE
OFFICIAL STATE FOSSIL, AND AMENDING TITLE 41, CHAPTER 4.1, ARTICLE 5, ARIZONA REVISED STATUTES, BY ADDING SECTION 41-853.

Be it enacted by the Legislature of the State of Arizona:
Section 1. Title 41, chapter 4.1, article 5, Arizona Revised Statutes, is amended by adding section 41-853, to read:
41-853. State fossil
PETRIFIED WOOD, OR ARAUCARIOXYLON ARIZONICUM, IS THE OFFICIAL STATE FOSSIL.

Petrified wood from Petrified Forest National Park.
Image taken by me.

Petrified wood is not actual wood, however it was wood at one point. Petrified wood is a fossil that formed from pieces of wood that have been mineralized. Mineralization is a process where groundwater moves through the wood and replaces all of the wood molecules with molecules of other substances, most often silica (i.e. quartz). This means that petrified wood actually isn't wood anymore, but a fossil of the former wood.

The specific species of petrified wood (Araucarioxylon arizonicum) that is the Arizona state fossil is an extinct conifer (like an evergreen) that can been found throughout Arizona and New Mexico. There is a problem with the state fossil though; the original name of the species was based on three different species. This means that although one of the three was correct, two had to be renamed, resulting in several of the trees identified since the initial 1889 description were likely named incorrectly. The problem is that proper identification can only be made with thin sections and close analysis, which is not likely going to happen for a majority of the samples previously identified, at least not any time soon. Arizona is host to one of the largest assemblages of petrified wood logs, with ~20% of all the petrified wood in northeastern Arizona found in Petrified Forest National Park. The concentrations of logs in Petrified Forest was a result of a log jam that flowed down a prehistoric river. The logs where then quickly buried, which allowed the mineralization process to proceed on the logs, converting them into fossils.

State Metal: Copper

CHAPTER 77

S. B. 1441

AN ACT AMENDING TITLE 41, CHAPTER 4.1, ARTICLE 5, ARIZONA REVISED STATUTES, BY ADDING SECTION 41-860.03; RELATING TO STATE EMBLEMS.
Be it enacted by the Legislature of the State of Arizona:
Section 1. Title 41, chapter 4.1, article 5, Arizona Revised Statutes, is amended by adding section 41-860.03, to read:
41-860.03. State metal
COPPER IS THE OFFICIAL STATE METAL.

An example of native copper.
Photo courtesy of the Flandrau Science
Center at the University of Arizona.

Copper is an elemental metal mineral, meaning that it is entirely composed of one element; copper (Cu) in this instance. It is also the only elemental metal, besides gold, which is not naturally silver or grey. Copper is the oldest known metal to have been manipulated by humanity. The Copper Age took place after the Neolithic (Stone) Age, and lasted from ~4500 BC to ~3500 BC, overlapping with the early Bronze Age. The earliest known Middle Eastern artifact is also made of copper, a pendant dating back to 8700 BC. In the modern day, copper is the third most consumed industrial metal in the world. Mining of copper in the US began with high grade ore deposits found in Arizona and Michigan in the late 1800's, however newer processes that were able to filter the copper out of low-grade deposits made excavating low-grade ores more economical, leading to more abundant uses of strip and open-pit mining for the recovery of copper. These processes enabled the US to become one of the leading producers of copper in the world.

Arizona's metallic mining map from the
Arizona Geological Survey.

In the late 1600's, Spanish explorers traveled the west looking for metallic deposits, specifically gold and silver. The association of these metals with copper enabled them to discover numerous copper deposits as well, even though it was not their primary focus. Eventually, the modern age of mining in Arizona was born in 1854 with the creation of the Arizona Mining and Trading Company in Ajo, AZ. Mining for copper was initially restricted to deep mine tunnels of fairly high quality ore. However, the success of the open-pit Bingham Mine in Utah illustrated that open-pit mining and new processing methods for low-grade copper ore worked well and Arizona began using similar processes, increasing their copper yield significantly. Currently, copper is the most valuable metallic commodity in Arizona, followed by gold, silver, molybdenum, and lead. In 2017, the US produced 1.27 million tons of copper with 68% of that coming from Arizona. There are currently over 3,000 Arizona locations that have copper listed as a commodity. These metallic deposits form a northwest to southeast band across the state (as seen on the map to the left). Along this band, most of the copper deposits are found within southeastern portion of the state (red on the map). These deposits are found mostly in granitic rocks that intruded within the region 70 to 55 millions years ago.