Please join us on April 20 at McFate Brewing Company.
Our speaker will be Dr. Jan Rasmussen presenting on Wulfenite in Arizona.
‘Wulfenite in Arizona’ by Jan Rasmussen
Arizona is famous for its spectacular wulfenite specimens, such as the butterscotch-colored, bladed crystals from the Glove Mine south of Tucson. A recent bill in the Arizona legislature has designated wulfenite to be the state mineral.
Wulfenite (lead molybdate) forms in the oxidized zones of lead-zinc-silver deposits during later periods of alteration. The best large samples of wulfenite are associated with Laramide (~75 Ma), Jurassic (~190 Ma), or mid-Tertiary (~25 Ma) lead deposits where there are permeable fault zones with open space, open channelways, or caves. Microscopic specimens of wulfenite are associated with the later stages of porphyry copper or other types of ore deposits in the lead-zinc zones. Surprisingly, wulfenite does not occur in the presence of molybdenite, but rather occurs in close proximity to cerussite (lead carbonate) that has been altered from galena.
Museum quality specimens of wulfenite occur at the Glove Mine in the northwestern Santa Rita Mountains of Laramide age and at the Silver Bill, Defiance, Mystery, and Tom Scott mines in the Turquoise district (Courtland-Gleeson area in Cochise County) of Jurassic age. Mid-Tertiary age wulfenite samples are found at the Red Cloud Mine in La Paz County, Rowley Mine in Maricopa County, Old Yuma Mine in the northern Tucson Mountains, and the Mammoth-St. Anthony Mine at Tiger, AZ north of San Manuel.
Dr. Jan Rasmussen is a consulting geologist in Tucson, specializing in writing permitting documents, such as Aquifer Protection Permits and Mine Plan of Operations, for consulting companies, such as SRK Consulting and other clients. As a Registered Geologist in Arizona and a Qualified Person with registration from SME, Jan has written Canadian National Instrument 43-101 reports for mining clients. Jan’s work in economic geology has included exploration for metallic and industrial mineral resources and most recently research with MagmaChem Exploration into ultra-deep hydrocarbon resources in the North Sea for a Norwegian oil company.
Jan earned a Ph.D. in economic geology from the University of Arizona in 1993 and then worked for Woodward-Clyde as a geochemist/economic geologist on the Yucca Mountain project in Nevada. Jan’s work there was recently published in the 2015 Geological Society of Nevada symposium volume.
Jan’s most recent full time job was as Curator of the Arizona Mining and Mineral Museum in Phoenix from 2007 through 2010. Jan received the SME Individual GEM award in 2010 for her work in educating children about the importance of mining in their lives. Her interest in wulfenite started with her early research into molybdenum in Arizona with the Arizona Bureau of Mines (now the Arizona Geological Survey).
Throughout her career, Jan has been committed to educating people about geology and has taught Physical, Historical, and Environmental Geology as adjunct faculty for the University of Arizona, Austin Community College, Cochise College, and Pima Community College.
Jan has coauthored 14 books or open file reports on Arizona geology and numerous articles, most of which are available as pdf files on her website www.janrasmussen.com. Jan has recently started a photographic website, www.MiningMineralMuseum.com about the Arizona Mining and Mineral Museum as it was in 2010.