Recent Work in Mineralogy and Petrology

Abstract

A MINERAL variously labelled johannite and uranopilite in collections has yielded to Messrs. E. S. Larsen and G. V. Brown the composition RO.UO₃.SO₃.4H₂O, where R = Cu,Fe,Na₂ (the American Mineralogist, vol. ii., p. 78, 1917). The new species thus indicated is called gilpinite, from the typical locality Gilpin Co., Colorado; but a Cornish specimen, one of those styled uranopilite, proves to be identical. The authors insist that optical tests under the microscope are characteristic, and that their application shows that more than one-third of the hundred specimens of “secondary uranium minerals” examined from various museums are incorrectly labelled.