Exposed to atmospheric influences it is more or less rapidly corroded, giving the familiar rust.
Pure lead is far more readily corroded than a metal contaminated with 1% or even less of antimony or copper.
The steam-chest is not used to such an extent, as the bottom would be prematurely corroded; less water is used, as the pulp would become too thin on account of the soluble salts (sodium chloride, sulphate, &c.) going into solution; and the roasted ore is not ground, as the hot brine readily dissolves the silver chloride from the porous ore, and thus brings it into intimate contact with iron and quicksilver.
The felspathoid minerals, sodalite, haiiyne and nosean, which crystallize in isometric dodecahedra, are very frequent components of the phonolites; their crystals are often corroded or partly dissolved and their outlines may then be very irregular.
All are built in the Doric style, of the local porous stone, which is of a warm red brown colour, full of fossil shells and easily corroded when exposed to the air.
Cables have frequently been picked up showing after many years of submergence no appreciable deterioration in this respect, while in other cases ends have been picked up which in the course of twelve years had been corroded to needle points, the result probably of metalliferous deposits in the locality.