Wulfenite, Arizona’s state mineral, is theme for current Tucson gem show


Date: Feb 12, 2019

Wulfenite — Arizona’s official state mineral — is the theme for this year’s 65th Annual Tucson Gem and Mineral Show, where exceptional specimens are on display from mines in Arizona and around the world.

Although classified as an uncommon mineral, wulfenite has wide distribution among the oxidized portions of lead-bearing deposits across Arizona.

It’s named in honor of Austrian mineralogist Franz Xaver von Wulfen, who researched and wrote about the Carinthia lead ores in the Bleiberg District in 1785.

Wulfenite crystals were originally called melinose, from the Greek word meli denoting honey, because of their honey-colored appearance.

Wulfenite, a molybdate of lead , is one of several principal molybdenum minerals including powellite, molybdite, molybdic ocher, ilsemannite and molybdenite. It is a secondary mineral found in open cavities of igneous rocks, the product of alteration found in upper oxidized portions of lead veins with commonly associated minerals including galena, pyromorphite and vanadinite.

Molybdenum is not a naturally occurring element. It always forms as part of a compound such as the commonly found ore molybdenite and also wulfenite. Its industrial qualities when alloyed with other metals such as steel and iron include strength, hardness and resistance to wear and corrosion. The hard silvery metal also has a high melting point — 4,800 to 5,560 degrees Celsius (8,600 to 10,000 degrees Fahrenheit). Molybdenite contains a compound of molybdenum and sulfur. Its molybdenum concentration is 60 percent compared to 26 percent molybdenum found in wulfenite. Wulfenite is lacking in deposits primarily composed of molybdenite, which is why it is not found in porphyry copper deposits. Its occurrence is linked more closely to lead (galena) deposits.

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