Arizona State Un-Official Mineral

Fire Agate

Arizona State Mineral: Fire Agate



Fire Agate is said to be Arizona's "Un-Official" State Mineral.

Fire Agate, a variety of chalcedony, is a semi-precious natural gemstone found only in certain areas of northern Mexico and the southwestern United States. Approximately 24-36 million years ago these areas were subjected to massive volcanic activity during the Tertiary Period. The fire agates were formed during this period of volcanism when hot water, saturated with silica and iron oxide, repeatedly filled cracks and bubbles in the surrounding rock.

Arizona State Un-Official Mineral: Fire Agate

Arizona State Mineral: Fire Agate

Fire agate (sometimes referred to as iridescent agate or rainbow agate) - to some people, this is a non-agate variety of chalcedony, containing inclusions of goethite or limonite, producing an iridescent effect. Chalcedony is a fibrous cryptocrystalline variety of quartz. Although its being called agate may have been based on the layered arrangement of the inclusions responsible for its iridescence, more likely it was so-named as a marketplace ploy. As this name suggests, some people see its overall appearance as resembling burning embers; it is multicolored. According to Sweaney (1979), these agates have come from several areas of the Sonora Desert region of northern Mexico and southern Arizona (e.g., on Saddle Mountain, near Tonopah, Maricopa County and near Safford, Graham County) and the Central Basin of Mexico; another well known locality is in the Black Hills of southern Riverside County, California. Within the last sixty years, making it the rarest and newest multicolored gemstone in the world. Gem quality Fire Agate is by far more rare than diamonds, emeralds or rubies.

The fire agates from Arizona come from the famous mines, such as Deer Creek, Slaughter Mountain, and others. These agates form in basalt and other volcanics, from a unique process wherein agate is layered in vugs from a hydrothermal solution, one micro-thin layer at a time. Some of these layers diffract light back in a rainbow pattern, creating brilliant bubbles and sheets of red, green, yellow, and the elusive blue.

A variety of agate containing inclusions of goethite or limonite, producing an iridescent effect. The layers are small enough that light entering them forms interference colors known as "fire." The gem is thought to be formed when hot water saturated with colloidal silica and iron oxide invades cavities in country rock and begin to cool. Chalcedony with iron oxide begins to grow on any available surface (the iron oxide gives the basic brown color to the gem). As the solutions began to precipitate and grow layers of silica and iron oxide would be deposited depending on the relative level of those elements in solution and underlying conditions. These alternating silica and iron oxide layers (Schiller layers) cause the brilliant fire in the gem. As iron oxide ran out in the solution colorless chalcedony continued to grow.


Arizona State Mineral: Fire Agate

Fire Agate is known for its healing qualities as well as its connection to the energies of the earth. It benefits sexual endeavors. It is be beneficial in healing problems with the stomach and endocrine system.

Legend has it among some people who love Fire Agate, that it possesses a "special energy" that can be felt when the stone is worn or held in the hand.

General Quartz Information

Chemical Formula: SiO2

Composition:  Molecular Weight = 60.08 gm

Silicon:    46.74 % Si  100.00 % SiO2
Oxygen:  53.26 % O
Total:    100.00 %   

Empirical Formula: (SiO2)

Environment: Sedimentary, metamorphic, and igneous rocks.

IMA Status: Approved IMA 1962

Locality: Found world wide

Name Origin: From the German "quarz", of uncertain origin

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