ANGLESITE, a mineral consisting of lead sulphate, PbSO,, crystallizing in the orthorhombic system, and isomorphous with barytes and celestite. It was first recognized as a mineral species, in 1783, by Dr. Withering, who discovered it in the Parys copper mine in Anglesey ; the name anglesite, from this locality, was given by F. S. Beudant in 1832. The crystals from Anglesey are small in size and simple in form ; they are brownish-yellow in colour, owing to a stain of limonite. Crystals from some other localities, notably from Monteponi in Sardinia, are transparent and colourless, possessed of a brilliant adamantine lustre, and numerous faces. The hardness is 3 and the specific gravity 6.3. There are distinct cleavages parallel to the faces of the prism (I 1o) and the basal plane (001), but these are not so well devel oped as in the isomorphous minerals barytes and celestite. Angle site is a mineral of secondary origin, having been formed by the oxidation of galena in the upper parts of mineral lodes, where these have been affected by weathering processes.