At the Emily coal pit, Arniston, Midlothian, a heap of shaly refuse from the workings became spontaneously ignited some time ago, the cause being presumably the evolution of heat by atmospheric oxidation of iron-pyrites. As a result of the slow combustion of the shale, accompanied as it is by liberation of sulphuric vapours, a number of uncommon mineral-species have been formed and deposited as sublimates in the cooler parts of the heap. The credit of discovering these minerals and recognizing their unusual character belongs to Mr. A. Craig Christie, F.L.S., from whom the specimens in the Royal Scottish Museum were obtained.