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Wulfenite

Occurs in Pinal County. Common in Arizona.

Chemical Formula: Pb(MoO4)

Specific Gravity: 6.5-7.0

Luster: Adamantine to resinous

Hardness: 2.5-3

Wulfenite is a lead molybdate mineral that often appears as bright orange to red crystals or masses. It is found in the oxidation zones of lead-molybdenum deposits. Made Arizona’s state mineral in 1986.

Next Pinal County mineral: Wurtzite

The Golden Gem of the Desert

Wulfenite, Arizona’s state mineral, is a vibrant golden color and brilliant crystal formations. It has captured the hearts of collectors and enthusiasts for centuries. Wulfenite is an important ore of lead and molybdenum and is found in various localities around the world.

Geological Formation and Occurrence of Wulfenite

Wulfenite (PbMoO4) is a lead molybdate mineral that typically forms as a secondary mineral in the oxidation zone of lead ore deposits. It is most commonly found in association with other lead-bearing minerals, such as galena, cerussite, and anglesite.

Wulfenite forms through the oxidation of primary lead minerals, such as galena, in the presence of molybdenum-bearing fluids. As these primary minerals undergo weathering near the Earth’s surface, they release lead and molybdenum ions into the surrounding environment. These ions then react with oxygen and other elements to form wulfenite.

Wulfenite crystals are typically tabular or pyramidal in shape and their color ranges from pale yellow to bright orange or red-orange. The golden yellow variety of wulfenite is the most prized by collectors and is often found in association with calcite, barite, and limonite.

Mineralogical Properties of Wulfenite

Wulfenite’s most striking feature is its vibrant golden color, which can range from pale yellow to deep orange. The color is caused by the presence of lead and molybdenum in its crystal structure.

With a hardness of 2.75 to 3 on the Mohs scale, wulfenite is relatively soft and delicate compared to other minerals. Its luster is resinous to adamantine, and its streak, the color left behind when the mineral is scratched on an unglazed porcelain plate, is white.

Wulfenite crystallizes in the tetragonal crystal system, forming square or rectangular tabular crystals with pyramidal terminations. Its crystals often exhibit perfect cleavage along one direction, making them fragile and susceptible to breaking.

Historical and Cultural Significance

The mineral was first discovered in the 18th century and was named after the Austrian mineralogist Franz Xaver von Wulfen. It was declared the state mineral of Arizona in 1986.

Wulfenite in the World of Minerals and Collectors

Wulfenite is highly prized by mineral collectors and enthusiasts for its captivating color and unique crystal formations. Specimens of wulfenite are sought after by collectors around the world and can command high prices depending on their quality, size, and location of origin.

Wulfenite crystals from famous localities, such as the Red Cloud Mine, La Paz County, Arizona, are particularly prized for their vibrant color and exceptional clarity. These specimens often grace the collections of museums and private collectors, adding to the allure and desirability of wulfenite as a collector’s gem. The mine is sometimes open to collectors.

Wulfenite as a Window to Earth’s Past

Beyond its aesthetic appeal and commercial value, wulfenite serves as an essential tool for geologists and mineralogists to understand the Earth’s geological history and the processes that have shaped its surface. Studying wulfenite and its association with other lead and molybdenum minerals provides insights into the oxidation of primary lead ores and the formation of secondary minerals in the Earth’s crust.

By examining the crystal structure and chemical composition of wulfenite, geologists can reconstruct the environmental conditions that prevailed during its formation, such as the presence of lead and molybdenum-bearing fluids near the Earth’s surface.

Conclusion

Wulfenite, with its captivating golden color and exquisite crystal formations, stands as a gem of the Earth’s abundance and geological beauty. Formed through the oxidation of primary lead ores, wulfenite’s vibrant hue has enchanted civilizations for centuries, adorning their art, talismans, and healing rituals.