This mineral, lead dioxide, does not seem to have been examined since it was first noticed by Breithaupt and Plattner in 1837 (Journ. pr. Chem. x. 508). This specimen, named "Schwerbleierz," is said to be probably from Leadhills, and the mineral is called, in the manuals of Dana and others, a doubtful species. It was named Plattnerite by Haidinger and subsequent authors.

A short time ago my friend Mr. Thos. Davies, F.G.S., of the British Museum, asked me to analyse a mineral from Leadhills, Lanarkshire, which he had had in his possession for some years, but the examination of which he had, from various causes, frequently postponed. On examination it was found to be lead dioxide—Plattnerite.