Introducing the Mineral of the Month series
Introducing the Department of Geosciences "Mineral of the Month" series. On or around the 1st of every month, curator Christopher Holl will select a speciment from the department's mineral collection, write a brief description, and publish the record to our newsfeed.
We begin the series with the mineral:
|Locality Nickname||Fairfield, Utah|
|Min Dat Locality Page||http://www.mindat.org/loc-4148.html|
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|About the Collection||http://www.princeton.edu/geosciences/about/mineral-collection/|
This is of the “crown jewels” of the Gem and Mineral collection, a large and very fine cut Variscite nodule from the Little Green Monster Mine in Clay Canyon, near Fairfield, Utah. Arthur Montgomery (’31) worked the now-closed mine in the mid 1930s with his partner Ed Over, and several decades later generously donated this specimen to the collection. These nodules were deposited as pure blue-green variscite (hydrous aluminum phosphate, AlPO4 · 2H2O) in brecciated limestone. Later, colorful alteration products formed along fluid-containing cracks in the variscite. Here we see yellow crandallite (hydrous calcium aluminum phosphate, CaAl3(PO4)2(OH)5 · H2O) and gray wardite (hydrous sodium aluminum phosphate, NaAl3(PO4)2(OH)4 · 2H2O). There are likely other rare minerals in this specimen in smaller quantities.