Turquoise is a hydrated copper aluminum phosphate mineral that forms in arid regions when water carrying copper and aluminum deposits filters through rock. This process primarily occurs in the American Southwest, making the United States a globally significant source of the stone. The gemstone holds deep cultural and economic importance, particularly for the Indigenous peoples of the Southwest who have mined and used it for over a thousand years. The stone’s color, which ranges from sky blue to green, has long symbolized the connection between the land and the sky. Although turquoise is found globally, the material sourced from the American West is distinctively tied to the region’s history and geology, making it a highly sought-after commodity.
The Primary Turquoise Producing States
The majority of commercially viable turquoise deposits in the United States are concentrated within the Southwestern states of Arizona, Nevada, New Mexico, and Colorado. This concentration is due to the area’s geological conditions, which feature extensive copper deposits and the necessary arid climate for the mineral to form.
Arizona, historically and currently, has been one of the top producers, often yielding turquoise as a byproduct of large-scale copper mining operations. The state is home to the Kingman mine, one of the largest and longest-running full-time turquoise operations, known for its bright blue stones and “water web” matrix. Another famous Arizona source was the Sleeping Beauty mine, which produced a highly prized, pure sky-blue turquoise with little to no matrix until it ceased operations in 2012.
Nevada has the greatest number of individual turquoise deposits, with over 100 mines and prospects having produced material over the last century. Key mining districts include the Royston area, which encompasses mines like Easter Blue and is known for stones that display a wide spectrum of colors from deep blue to various greens. The state is also the source of the extremely rare and valuable Lander Blue and Number 8 turquoises, both of which are celebrated for their distinctive spiderweb matrix patterns.
New Mexico was the largest US producer until the 1920s, with a history of mining stretching back to prehistoric times. The Cerrillos Hills, located south of Santa Fe, are an ancient mining site recognized for their historical significance, though modern commercial production is limited. Colorado’s production has been historically smaller but includes notable sites like the King’s Manassa mine. This mine is recognized for producing stones that often have a distinct blue-green color running through a hard, golden-brown host rock.
Distinguishing Characteristics of American Turquoise
American turquoise is identifiable by specific mineralogical traits that distinguish it from international stones. The most striking characteristic is the presence of the matrix, which is the remnant of the surrounding host rock appearing as veins or webbing. This matrix is composed of materials like limonite, sandstone, or iron pyrite. When it forms a thin, intricate pattern, it is referred to as a “spiderweb” matrix, a feature highly valued in American specimens.
The color spectrum of US turquoise is directly influenced by the trace elements present during its formation. A higher concentration of copper typically results in the clear, intense blue color, which is characteristic of many Arizona deposits. Conversely, the presence of iron impurities causes the stone to exhibit greener hues, a color variation more commonly associated with many Nevada mines. The hardness of turquoise, measured on the Mohs scale between 5.5 and 6.5, also varies; the harder, less porous stones generally have better color retention and take a superior polish.
Current Status of US Turquoise Mining
The current US turquoise supply is defined by scarcity, as many famous and prolific mines have been depleted or closed. Mines like Sleeping Beauty and Bisbee, known for their high-grade, distinctive turquoise, are no longer commercially active, making new material from these locations extremely rare. This limited availability has led to significant increases in price for authentic American turquoise.
While some mines, such as Kingman, continue to operate, a large percentage of the turquoise material extracted is lower-grade and requires treatment. The distinction between “natural” and treated turquoise is important to the current market, as natural stone has not undergone any enhancement process. Stabilized turquoise, which is the majority of the material available, is infused with an epoxy resin to increase its hardness and improve its color, making it more durable for jewelry use.