A team of geologists has discovered three new minerals — leesite, leószilárdite and redcanyonite — growing on the walls of old uranium mines in southern Utah.
Leesite, leószilárdite and redcanyonite are like uranium rust and while the glowing green stereotype of uranium is close it’s not quite right.
These three yellow minerals represent a small and unique slice of the Earth’s crust where human activity spurred the formation of previously unknown minerals.
All three specimens were uncovered by Travis Olds, a graduate student at Notre Dame University, Owen Mills, director of Michigan Tech’s Applied Chemical & Morphological Analysis Laboratory, and Shawn Carlson, an independent geologist.
“The only way to better understand the chemistry of uranium is to go out and find new minerals — and describe their topology, their structures,” Olds said.
“They teach us a lot about how uranium can then be moved in the environment.”
Though small and barely visible to the naked eye, leesite occurs in bright yellow aggregates of stacked blades or radiating needles up to one millimeter in length.
This mineral also forms powdery masses nestled against a backdrop of companion minerals, most notably gypsum.
Leesite’s atom arrangement stacks in alternates of uranium and oxide layers, and potassium is what sets it aside as a new mineral.
Given its chemistry and structure, it’s a member of the schoepite mineral family; miners called the general mess of these minerals growing on the tunnel floors ‘gummites.’
Leószilárdite is pale yellow. A carbonate formed through uranium ore interacting with air, it’s also water soluble. Its most distinctive feature are bladed crystals.
“If you look at leószilárdite in a picture, you can kind of pick out that they have an unusual shape,” Olds said.
“But put them under the scanning electron microscope and it’s obvious.”
Redcanyonite is named for the area where these rare minerals are found.
This mineral varies in hue from orange to red-orange and the color comes from what chemically makes the mineral new — manganese and ammonium in its structure — and being a sulfate, it is not soluble in water, unlike leószilárdite.
Redcanyonite is one of the rarest uranyl minerals known because it can only grow within narrow constraints: access to manganese ions is the main driver, but it also can only form in organic-rich layers, the most likely source of ammonium.
The new minerals are described in the December 2016 issue of the Mineralogical Magazine.
U. Hålenius et al. 2016. New minerals and nomenclature modifications approved in 2016. Mineralogical Magazine 80 (7): 1315-1321; doi: 10.1180/minmag.2016.080.086
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