Bobcookite, NaAl(UO2)2(SO4)4·18H2O, is a triclinic hydrous sodium aluminum uranyl sulfate. It occurs in medium- to coarse-grained sandstone, conglomeritic sandstone, and thick siltstones of the Shinarump Member of the Chinle Formation. It was found underground in the Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, and was described by Anthony R. Kampf et al. (2014). Bobcookite is a relatively rare mineral in the secondary sulfate mineral assemblage at the Blue Lizard mine. The mineral commonly occurs in massive veins and cavity fillings and as irregular columnar (crude prismatic) lime-green to greenish-yellow crystals, which are often more or less curved and sometimes composite. Columnar crystals are up to about 2 mm in length. Other secondary minerals found in direct association with bobcookite include boyleite, chalcanthite, gypsum, pickeringite, hexahydrite, johannite, and at least two other new uranyl sulfate minerals currently under study. Bobcookite is named in honor of Dr. Robert B. “Bob” Cook, former distinguished professor and head of the Department of Geology and Geography at Auburn University, Auburn, Alabama.
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