Six samples of biotite schist from a site near Pringle, South Dakota, contained from 140 to 750 parts per million lithium. These values are far greater than are found in mica schists in most of the rest of the southern Black Hills. The lithium may have emanated from concealed lithium pegmatite, and such pegmatite can be of interest as a possible source of rare minerals, especially tantalite and beryl. Whether making a full test of the anomaly will become economically judicious is much less clear.
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Lithium anomaly near Pringle, southern Black Hills, South Dakota, possibly caused by unexposed rare-mineral pegmatite