The Mineralogical Record article (Stolburg, C.S., 1984, The mines and minerals of Darwin, California, v15:5) gives an inconclusive old reference suggesting that stolzite was "reported". Tom Moore (2006) added more emphasis: "The "scheelite" specimens, often seen in older collections, were found for decades throughout the district, but probably the best are those which came from the Thompson mine, which ceased operations in 1976. It now turns out that these are not scheelite crystals after all, but something much more intriguing: determinative work done earlier this year at the Mackay School of Mines of the University of Nevada on a batch of old specimens has shown that all of the specimens—all of them in the tested batch, anyway—are stolzite pseudomorphs after scheelite. Since the appearance of all of the "scheelite" crystals on the old Darwin specimens is very much the same, it's at least quite plausible that all are actually stolzite pseudomorphs; these must therefore be counted as among the world's finest stolzites (if you do not hold the pseudomorphism against them), and such is your consolation for having to change your labels." It may be added that the transparent crystals which fluoresce blue white in short wave ultraviolet are probably unaltered and that the pseudomorphs are opaque dark gray.
Thompson Mine, Darwin Mine, Darwin, Darwin Mining District, Darwin Hills, Inyo County, California, USA